C4 and camaro sensor and relay/switch locations and info

grumpyvette · Nov 17, 2008

this infos bound to be helpful at times
READ THE THREAD THRU TO THE END AND BE AWARE IT, AND ALL OTHER THREADS ARE CONSTANTLY UPDATED WITH NEW LINKS AND INFO
without testing you simply guessing
never guess, deal in verified FACTS!
guessing is a waste of time
think logically, isolate and test

yes IM aware some guys would rather dig out their eye with a red hot fork than to read links, but if you take the time to actually research,pull the trouble codes and READ THRU the shop manual and, use diagnostic tools. like code scanners, and multi meter,timing lights, vacuum gauges etc,..... before jumping into "fixing" problems. in most cases youll find its far faster and easier to locate and correct the problem.
LOOK FOR LOOSE OR CORRODED ELECTRICAL WIRING CONNECTORS, in THE WIRING HARNESS, and VERIFY YOUR FIRING ORDER, YEAH I KNOW YOUR SURE ITS CORRECT, CHECK IT CAREFULLY AGAIN, YOUR NOID TEST LIGHT AND MULTI- METER CAN SAVE YOU A GREAT DEAL OF PROBLEMS AND SCRATCHING YOUR HEAD IF YOU TEST BASIC ELECTRICAL CONNECTIONS< RESISTANCE AND VOLTAGE, CHECK YOUR SENSORS AND GROUNDS, A SHOP MANUALS MANDATORY, HEAT SENSORS AND IGNITION MODULES AND OIL PRESSURE SENSORS HAVE A LONG TRACK RECORD OF FAILING OR PARTIALLY AND INTERMITTENTLY NOT FUNCTIONING
IM JUST CURIOUS?
how many of you gentlemen go to a computer, print out related wiring diagrams ,get out a multi meter and a shop manual and actually read the shop manual, and step thru the indicated testing procedures? check for voltage ohms resistance, loose connections, etc. and have actually used the shop manual, multi meter and printed wiring diagrams ans instructions to isolate and solve a problem on your car?

https://www.corvettecentral.com/c4-84-96/96-shop-service-manual-cd-rom-114143?returnurl=/c4-84-96/?count=9

if you have at lease 38 psi in the fuel rail, and it holds at or near at least 38 psi for at least a couple minutes after you stop cranking the engine, the fuel pressure regulator is most likely functioning correctly, but you state the injectors are not squirting fuel and the pump keeps running while you crank the engine?
you can test the electrical connectors on the injectors with a noid test light to watch the electric pulse,at each injector location, ID verify timing injector resistance,and check for vacuum leaks while testing, and remember theres a 9th cold start injector on the 1985-88 TPI fuel rail

first check your shop manual for the fuse and fuse able link locations
fuses are located in several locations and fuse-able links near the battery, NOW GET A MULTI METER AND CHECK ALL THE FUSES , AND GROUNDS AND BATTERY VOLTAGE AND ELECTRICAL CONNECTIONS LIKE BATTER CABLES AND SENSOR WIRE CONNECTIONS, BECAUSE A SURPRISING NUMBER OF PROBLEMS ON OLDER CORVETTES AND MUSCLE CARS ARE RELATED TO BLOWN FUZES, LOOSE OR CORRODED CONNECTORS, AND BAD BATTERY CONNECTION CABLES OR WEAL BATTERY'S OR DEFECTIVE ALTERNATORS
HERES A FEW USEFUL, related bit of info and LINKS YOU MIGHT WANT TO LOOK THRU
and yes they should all read very closely) then you need a noid kit for a G.M. fuel injection system, these are basically little lights that light as the injector pulse hits them that you plug into the injector harness,after you remove the harness from the injectors, they plug into the harness just like an injector, if you try to start the engine and they blink on and off the pulse is reaching the injectors thus proving that the injectors get the pulse, each injector should get a pulse and you should see each noid light flash, if you don,t theres an electrical or wiring issue, that must be addressed.
injectors normal state is CLOSED they open only with a electric pulse, the duration of the pulse controls the volume of fuel flow
carefully visually inspect your cars wire harness for corrosion ,loose or broken or shorting connectors or wiring, obviously getting the wrong electrical pulse, a grounded or shorted connector will cause problems.
a NOID light can be used to test, the pulse is intermittent if plugged into the cars wire harness and its more likely the injector needs cleaning

http://www.harborfreight.com/11-piece-n ... 97959.html

set up a multi meter like this and pull fuses one at a time to locate shorted circuits

replacement injector pig tails are available at rock auto for less than $5 each

read these links and
related sub links
pull trouble codes

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-84695

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=8895&hilit=start+sequence#p8895

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/

http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/#post-71867

http://garage.grumpysperformance.com/index.php?threads/1990-corvette-no-spark.13857/#post-70888

http://garage.grumpysperformance.com/index.php?threads/diagnoseing-tpi-lt1-problems.1241/

reading links and sub links can help
replacement connectors and pigtails are available

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.co...-auto-elecrtrical-connectors.3105/#post-68805

http://garage.grumpysperformance.co...cting-a-distributor-for-your-application.855/

http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46397

viewtopic.php?f=36&t=3105&p=8272&hilit=connectors+pigtails#p8272

viewtopic.php?f=32&t=168&p=41767&hilit=connectors+pigtails#p41767

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-17654

reading thru a few links might be helpful
step #1
always ISOLATE AND VERIFY, TEST EVERYTHING ASSUME NOTHING!
IF YOU skip the links and you'll miss a good deal of useful info
ANY TIME YOU SUSPECT FUEL INJECTOR OR FUEL SYSTEM RELATED ISSUES ,A REASONABLE START POINT IS TO USE A GOOD QUALITY FUEL INJECTION CLEANER ADDITIVE IN THE FUEL TANK AND SWAP TO A NEW FUEL FILTER
http://www.bgprod.com/catalog/gasoline- ... m-cleaner/
http://www.bgprod.com/catalog/gasoline- ... m-cleaner/

AND YES AMAZINGLY, ACTUALLY READING THRU THE POSTED LINKS AND SUB LINKS might help

http://www.chevythunder.com/fuel%20inje ... pg%20B.htm

http://www.mainstreamtopics.com/forums/ ... iagnostic/

http://www.mamotorworks.com/corvette-c4 ... -6128.html

http://garage.grumpysperformance.co...start-right-back-up-and-run.10739/#post-46893

Intake Air Temp sensor. It is located on the bottom of the inlet plenum a few inches ahead of the distributor. It is like right next to the fuel pressure regulator., it can effect fuel flow rates

If your experiencing intermittent electrical issues you will obviously need to get out the shop manual for your year corvette, a multi meter and do some isolate and testing, but be aware that loose or corroded connections , will be hard to isolate, as they seldom present a consistent, solid open or dead short in the wire,theres several electrical connector plugs that connect thru the firewall near the battery location that are subject to corrosion issues and frame grounds that might be suspect, obviously theres sensors that can be defective.

links with lots of sub-links that should be useful, most guys ,faced with isolating an electrical issue, seem to get over whelmed, but if you get out the schematics, use a multi meter and some logic in tracing the circuits, and start pulling fuses and measuring resistance and voltage, take the time to read the manual ,pull trouble codes,and if required get a scan tool or a data logging program for your lap top computer, and using the shop manual, you can generally isolate the cause

http://forum.grumpysperformance.com/viewtopic.php?f=80&t=728&p=9217&hilit=+sensors+location#p9217

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=39419&hilit=+sensors+location#p39419

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=2697&p=29270&hilit=+sensors+location#p29270

viewtopic.php?f=50&t=8136&p=28980&hilit=scan+tool#p28980

viewtopic.php?f=27&t=3096&p=18612&hilit=scan+software#p18612

viewtopic.php?f=44&t=758&p=1087&hilit=opti+crap#p1087

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=168

viewtopic.php?f=2&t=3074&p=8144#p8144

viewtopic.php?f=36&t=3222&p=8575&hilit=test+alternator#p8575

viewtopic.php?f=70&t=3504&p=9220#p9220

viewtopic.php?f=36&t=8493&p=29779#p29779

viewtopic.php?f=44&t=3401&p=8972&hilit=test+alternator#p8972

viewtopic.php?f=55&t=1241&p=3037&hilit=test+alternator+coil+test#p3037

viewtopic.php?f=50&t=609&p=810&hilit=test+alternator+coil+test#p810

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=596

http://scehovic.angelfire.com/C4starts.html

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=4683

http://shbox.com/1/component_location_views.html

http://www.smogtips.com/trouble-codes.cfm

http://www.aa1car.com/library/us796obd.htm

viewtopic.php?f=57&t=2538&p=6984#p6984

viewtopic.php?f=32&t=2697&p=6985#p6985

viewtopic.php?f=36&t=768&p=2394&hilit=+manual#p2394

viewtopic.php?f=36&t=520&p=645&hilit=vats+resistor#p645

don,t get over whelmed,
simply break the problem down to testing each basic sub system,
test each related sensor and electrical component and electrical sensor and connection.

some reading on the threads posted below, a bit of logic and deductive reasoning, and a multi meter and a shop manual will go a long way toward finding and fixing the problem.

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

sensor locations

Mass Air Flow (MAF), mounts in intake ducting between air filter and throttle body.
Throttle Position Sensor (TPS), mounts on right side of throttle body.
Idle Air Control valve (IAC), mounts in small manifold on bottom of throttle body.
MAF power relay, in relay center on firewall beside master cylinder.
MAF burn off relay, in relay center on firewall beside master cylinder.
Manifold Air Temperature sensor (MAT), mounts in bottom of plenum near the back
Coolant Temperature Sensor (CTS), mounts on front right of intake manifold base, below IAC valve
Cold start switch, front right of intake manifold base, below CTS
Exhaust Gas Recirculation valve(EGR), on top of intake manifold base, centered under plenum
EGR solenoid, on top of intake manifold, rear, between distributor and valve cover.
EGR diagnostic switch, on base of EGR valve.
Electronic Spark Control (ESC)knock sensor, bottom right of engine block, in front of starter just above oil pan rail, in the coolant drain boss.
ESC module, in relay center on firewall beside master cylinder
Electronic Spark Timing (EST) module, on distributor.
Oxygen (O2) sensor, in left exhaust manifold.
Air Injection Reactor (AIR) convertor divert solenoid and port solenoid, both together at front of right valve cover.
Oil pressure switch, on Y fitting with oil pressure gauge sender mounted in the oil pressure boss on the top left rear of the engine block behind intake manifold base. (applies power to fuel pump if fuel pump relay or relay circuit fails).
Fuel pump relay, in relay center on firewall beside master cylinder.
Fuel vaper canister (charcoal can) solenoid, on top of charcoal can in front left corner of engine bay.
Air Conditioner (AC) pressure switch, in boss on AC high pressure side aluminum tube beside right strut tower.
vehicle speed sensor, back of speedometer.
Cooling fan relay, on core support beside battery.

Sensor Locations

knowing whats going on and WHY can help

http://www.corvettefever.com/techarticl ... index.html

http://members.shaw.ca/corvette86/Component Location View 86.pdf

http://members.shaw.ca/corvette86/FuelSystemDiagnosis.pdf

http://www.summitracing.com/parts/HYP-4026/

http://www.summitracing.com/parts/HDA-3653/
Sensor
Location

Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.

Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.

viewtopic.php?f=54&t=1396&p=3221&hilit=+switch#p3221

Oil Pressure Sender/Switch. Top, left hand rear of engine.

Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.

MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.

Outside Temperature Sensor. Right side of engine, top right corner of radiator.

In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.

MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.

http://tpiparts.net/85_89_maf_sensors/

Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.(some years have two ,one on both sides)

TPS (Throttle Position Sensor). Right side of throttle body at the front.

Sensor Outputs:

Sensor
Measured Value

Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.

Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.

Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.

Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.

MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.

Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.

In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.

MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.

TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

IAC and TPS Adjustment
http://www.thirdgen.org/tpimod2

TPI Injector Swap
http://www.thirdgen.org/injectorswap

Throttle Body Coolant Bypass
http://www.thirdgen.org/coolantbypass

http://www.jcwhitney.com/autoparts/Sear ... p=ZX503796

http://www.summitracing.com/parts/SUN-CP9001

http://www.etoolcart.com/autoxray-scann ... x6000.aspx

viewtopic.php?f=32&t=304

ID also suggest buying a diagnostic tool, with real time data logging to a lap top computer, and your shop manual, it helps isolate problems, ignition spark should be bright blue and impressive, if its, weak,narrow, yellow or red theres a problem so research the cause, verify the coil and voltage

the oil system sensors are all well known potential sources for oil leaks ,and ignition problems as a defective sensor, cuts off the ignition,
READ THE LINKS
but the two blade sensor on the rear of the block, near the distributor base on the early c4 is a known , frequently defective part, and not only will it leak oil, if the switch is defective the fuel pump operation is random or not functional, it will also as it goes defective give intermittent or oil pressure readings that fluctuate.
if you start seeing oil on the rear of the block, its not always a defective rear seal , loose oil filter or loose defective rear intake manifold gasket, check the sensors near the distributor base.

http://www.ecklers.com/corvette-oil-pressure-sender-1985-1987.html

http://www.ecklers.com/corvette-fuel-pump-switch-oil-pressure-sender-1989-1996.html

Corvette Fuel Pump Switch/Oil Pressure Sender, 1989-1996

Corvette Oil Pressure Sender, 1985-1987
http://www.ecklers.com/corvette-oil-pressure-sender-1985-1987.html?crosssell=Product_Viewed

Corvette Oil Temperature Sensor, 1990-1996
http://www.ecklers.com/corvette-oil-temperature-sensor-1990-1996.html

THE DIAGRAM ABOVE HAS THE CORRECT WIRE COLORS

BTW FAULTY GROUNDS, IN MANY CARS AND ESPECIALLY NEWER CORVETTES CAUSE MANY ELECTRICAL ISSUES SO IF YOU HAVE INTERMITTENT ELECTRICAL ISSUES CHECK THEM CAREFULLY

LCD dash ground is behind drivers kick panel . There are also several electrical grounds down just above the oil filter and one behind the passenger kick panel for the ECM. and a couple on the rear of the drivers side cylinder head, Grounds are a constant issue on most c4's. Hope this helps.

grumpyvette · Nov 29, 2008

Re: C4 sensor info

you really need a old computer, an ADL cable and software to read the info and of course a shop manual for YOUR YEAR CORVETTE, and a MULTI METER
reading links may seem like a waste of time , but having a shop manual, a decent up-to-date, scan tool and a multi meter and a good understanding of what your testing and why your testing it helps a great deal
like the old saying how do you eat an elephant ?......one little bite at a time!

all the answers are readily available, theres known testing procedures and listed test results you can expect, and procedures listed in the shop manual for isolating and testing components, you don,t need to be a genius, you just need to be logical and persistent and not afraid to learn new things while getting your hands dirty at times, don,t get overwhelmed , break everything down too easy individual problems and tests, verify and test all the sensors,and test for factors like consistent fuel pressure, known temps,expected voltage or ohms resistance, and vacuum readings and don,t randomly start replacing parts as that gets expensive and its rarely the most efficient way to eliminate problems(unless you get really lucky) with modern computer diagnostic software you,ll have some advantages but think logically, most automotive problems still concern, compression, fuel delivery ,fuel pressure, vacuum, temperature or electrical issues.
and posting clear pictures of each spark plug labeled as to its cylinder number,
doing a vacuum leak test,do a fuel rail pressure test
do a compression test getting the compression number from each cylinder
check voltage on the coil input lead and alternator
http://www.helminc.com/helm

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.
Here's some flow figures, right off the manufactures sites in many cases. Keep in mind the concept of the chains weakest link. It does ABSOLUTELY no good to match a base or runners on a TPI intake that flows 250cfm if the other part flows 200cfm. You'll still only flow 200cfm. The HOLLEY STEALTH RAM FLOWS at 275cfm out of the box,(minor port clean-up work) and can easily reach 300cfm with minor port work. The stock TPI has a hard time flowing 230cfm even with minor port work. Look here. Most of this info is right off the Accel, Holley, Edelbrock, and TPIS sites. Add a little math and the results become much clearer!!!

Intake......runner length .... port in...... out
Stock GM Base----- 6.375"------------- 1.47"------- 1.96x1.20
TPIS base------------6.125"------------- 1.75"------- 2.09x1.28
Accel base-----------6.125"------------- 1.75"---------2.09x1.28
Holley base--------- 6.000" ------------ 2.30â€-------- 1.90x1.23 (2.337 sq inches)

Runners
Stock TPI-------- 7.250"------1.470" round(1.70 sq inches)
SLP -------------- 6.625"------1.600" round (2.01 sq inches)
Accel LTR------- 6.625"------1.615" round (2.05 sq inches)
TPiS-------------- 7.625"------1.660" round (2.168 sq inches)
Mini ram --------3.500â€
stock MRII with 1204 (AFR 195) ports, 58MM - 265 cfm
stock MRII with 1206 (AFR 220) ports, 58MM - 281 cfm
MRII clean-up, 1206 ports, 58MM - 292 cfm
MRII cut, weld, port, etc, 58MM - 321 cfm
LT1 ----------3.000â€

Runners (measured individually)
Stock........................................................................................................................................203.17 cfm
ACCEL.....................................................................................................................................242.02 cfm
Extrude/ACCEL........................................................................................................................275.83 cfm
Super Ram................................................................................................................................289.18 cfm
Intake manifold with 3/8 inch radiused inlet .............................................................................222.45 cfm
Holley stealth ram â€¦â€¦â€¦..........................................................................................................275.00 cfm

Stock intake manifold with runner
Stock.........................................................................................................................................198.72 cfm
ACCEL......................................................................................................................................213.52 cfm
Extrude/ACCEL.........................................................................................................................217.11 cfm
Super Ram.................................................................................................................................220.67 cfm
Holley stealth ram â€¦.................................................................................................................275.00 cfm
ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.....................................................251.51 cfm
ACCEL Hi-Flow intake manifold with runner Stock...................................................................215.83 cfm
ACCEL......................................................................................................................................232.53 cfm
Extrude/ACCEL.........................................................................................................................243.21 cfm
Super Ram.................................................................................................................................240.24 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.............................275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner.......................................266.94 cfm
Edelbrock Performer RPM manifold (Stock)...............................................................................286.51 cfm
Edelbrock Victor Jr....................................................................................................................275.24 cfm

Runner Length

Stock TPI manifold ...................8â€ ...............runners 11.25â€............... cylinder head 6â€.............total 25.25â€
Accel super ram manifold........ 8â€................runners 7.00â€............... cylinder head 6â€............ total 21.00â€
Holley stealth ram manifold .....6.26â€ ................................................. cylinder head 6â€............ total 12.26â€
Edelbrock performer RPM ...........................runners 6.00â€................ cylinder head 6â€............ total 12.00â€
Edelbrock Victor Jr .......................................runners 5.50â€................ cylinder head 6â€............ total 11.50â€

Now playing with the figure in the calculators below, what you'll find is that if your using a 350 size engine as a guide, the tpi runner length is ideal for peak tq 3427rpm and 2700-4000rpm for peak hp.

The Accel Super Ram is ideal for peak tq at 4032rpm and 3300rpm-4800rpm for peak hp.

Holley's Stealth Ram runner length is ideal at 4700 for peak tq and 5618rpm to 6282rpm for peak hp.

The TPIS Mini Ram and LT1 intakes are ideal for peak tq at about 5200rpm and 7244rpm to 8101rpm for peak hp.

By hp peak, in the above lists, I'M REFERRING TO THE RPM RANGE WHERE combination of cross sectional area MATCHED TO THE plenum to INTAKE valve distance WHERE THE internal AIRFLOW HARMONICS TEND TO INCREASE THE CYLINDER FILLING EFFICIENCY (WHERE THE INTAKE WILL TEND TO PULL THE MOST HP). Now KEEP FIRMLY IN MIND the engines tend to enter valve float and get close to engine red line by 6300-6700rpm depending on your combo. After running all the available combos, I've found a HOLLEY STEALTH RAM has been EXTREMELY EFFECTIVE on several engines tested. CURRENTLY THE STEALTH RAM SEEMS TO
BE THE CHOICE, ESPECIALLY IF MATCHED TO GOOD CYLINDER HEADS AND THE CORRECT
CAM.

OBDI code scanner adapter driver
http://www.1320electronics.com/16pin_ALDL_BT_USB_MK2.html

http://www.1320electronics.com/products.html

https://play.google.com/store/apps/details?id=com.sgiroux.aldldroid&hl=en

$90

watch video

bytor said:
Came across this info while doing some research and thought I'd share.

http://www.hobracing.com/tech/tpi_flow.asp
TPI Intakes and runners

The following airflow tests were performed on the University of Northwestern Ohio's SuperFlow SF600 Flow Bench. All CFM values are corrected for airflow at 28 inches of water. Injector flow rates are flowed at 43.5 PSI on an injector flow bench using test fluid with same density as gasoline.

AirFlow

Stock TPI/LT1 48mm Throttle Body w/o airfoil -- 783.0 cfm

Stock TPI/LT1 48mm Throttle Body w/ airfoil -- 821.9 cfm

TPI/LT1 52mm Throttle Body w/o airfoil -- 848.9 cfm

TPI/LT1 52mm Throttle Body w/ airfoil -- 898.8 cfm

Stock 98 Camaro 3800 II Throttle Body -- 554.3 cfm

Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm

Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm

Stock 87 GN 3.8L Turbo AC MAF sensor w/ screen -- 584.2 cfm

Stock 86 2.8L AC 5-wire MAF sensor w/ screen -- 576.2 cfm

Stock 96-up AC 3100 V6 MAF sensor w/ screen -- 616.4 cfm

Stock 96-up AC 3100 V6 MAF sensor w/o screen -- 670.7 cfm

Stock 94-up LT1 MAF Sensor w/o screen -- 719.0 cfm

Stock 85-87 Firebird TPI airbox mid piece -- 499.3 cfm

Stock 4.3/5.0/5.7 2bbl TBI complete -- 574.1 cfm (dry)

Stock 4.3/5.0/5.7 2bbl TBI w/o injectors -- 584.7 cfm

Stock 3800 vin L throttle body w/ screen -- 419.1 cfm

Stock 3800 vin L throttle body w/o screen -- 444.8 cfm

4bbl MPFI Holley Throttle Body -- 1287.6 cfm

Another source sent in these flow numbers

Flow and HP ratings for Throttle-bodies:

Flow (cfm) Max. NA HP
Stock 668 300
Stock w/airfoil 710 350
52MM w/airfoil 835 400
54MM (AS&M) 900 450
58MM 1050 500

TPI Intakes and runners flow rates

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm

the stock TPI has a hard time flowing 230cfm even with minor port work, look here
most of this info is right off the accel,holley,edelbrock, and TPIS sites, add a little math and the results become much clearer!!!

Intake....... length ....... port in -- out
Stock GM Base--- 6.375"------ 1.47"- 1.96x1.2
TPiS base------ -6.125"------ 1.75"- 2.09x1.28
Accel base----- -6.125"------ 1.75"- 2.09x1.28
Holley base------- 6” runner 2.3”- 1.9”x 1.23 (2.337 sq inches)
Runners
Stock TPI----- -- 7.250"------1.470" round(1.70 sq inchs)
SLP ----------- - 6.625"------1.600" round (2.01 sq inchs)
Accel LTR------- 6.625"------1.615" round (2.05 sq inchs)
TPiS----------- 7.625"------1.660" round (2.168 sq inchs)
Mini ram -----3.5”
LT1 ----------3”

Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet.............................222.45 cfm
Holley stealth ram ………..275cfm

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm
Holley stealth ram …..275cfm

ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.........251.51 cfm

ACCEL Hi-Flow intake manifold with runner
Stock....................215.83 cfm
ACCEL................232.53 cfm
Extrude/ACCEL....243.21 cfm
Super Ram............240.24 cfm

Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet ...............275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner ..............266.94 cfm
Edelbrock Performer RPM manifold (Stock)..........286.51 cfm
Edelbrock Victor Jr. ............275.24 cfm

HOLLEY STEALTH RAM
the HOLLEY STEALTH RAM FLOWS at 275cfm out of the box, and has the potential when matched to the correct heads and cam to totally out flow most other intakes available,can easily reach 300cfm with minor port work and costs much less
Stock…………………………… 275cfm
Ported…………………………..300cfm

Runner lengths
Stock tpi manifold 8” runners 11.25”, cylinder head 6” total 25.25”
Accel super ram manifold 8” runners 7” cylinder head 6” total 21”
Holley stealth ram manifold 6.26” ” cylinder head 6” total 12.26”
Edelbrock performer RPM runners 6” ” cylinder head 6” total 12”
Edelbrock vic jr , runner length 5.5” ” ” cylinder head 6” total 11.5”

Also interesting TPI mods. Not so sure I agree with the one on bumping up the initial timing.
http://www.hobracing.com/tech/tpi_mods.asp
useful related info
http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.com/index.php?threads/code-scanners-software.3096/#post-18612

http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/

http://garage.grumpysperformance.co...too-common-questions-can-be-found-here.12892/

http://garage.grumpysperformance.co...eight-trouble-code-scanners.11056/#post-49140

http://garage.grumpysperformance.com/index.php?threads/odbii-scanners.9697/#post-36100

http://garage.grumpysperformance.co...ittent-cylinder-miss-problem.9478/#post-34812

http://garage.grumpysperformance.co...an-obdii-reader-analizer-ect.8136/#post-29345

http://garage.grumpysperformance.co...h-flicker-on-dash-and-radio.13593/#post-70202

Last edited: Yesterday at 3:57 PM

info that might help (before you ask, yeah the LT1 is very similar)

L-98 Engine Start Sequence

knowing whats going on and WHY can help

http://members.shaw.ca/corvette86/Component Location View 86.pdf

http://tpiparts.net/85_89_maf_sensors/

http://members.shaw.ca/corvette86/FuelSystemDiagnosis.pdf

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions. ignition spark should be bright blue and impressive, if its, weak,narrow, yellow or red theres a problem so research the cause, verify the coil and voltage

Fuel Rail Pressurization:

When you first turn the key to the â€œonâ€ position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driverâ€™s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you canâ€™t make at least 4 PSI oil pressure. This is a â€œlimp home modeâ€ feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will â€œcatchâ€.

Engine "Catches":

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensorâ€™s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more â€œon timeâ€ or less â€œon timeâ€) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.
viewtopic.php?f=56&t=3049&p=8053#p8053

Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46030

Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

Theory of Operation

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

MAF Operating Conditions

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

MAF Problems

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

this flow chart might help

http://members.shaw.ca/corvette86/FuelSystemDiagnosis.pdf

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

MAF Mods

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.
Welcome to C4 vette codes it is very ....repeat very
important that if you are not savvy of working on your
vette ...you would be better off - taking your car to a
dealership for repairs on your trouble codes.
However if you feel that you want to dive right in ..than you
have come to the right place.First locate your car's alcl
this component is located just below the instrument panel and
to the left of the center console. Remove the plastic cover
the first two slots to your right are the A & B slots for a drawing of
the alcl module's picture is added below.
The A slot is the diagnostic slot and the B slot is the ground
slot. insert the computer key into these slots (with the engine
off) this is very important...now only put the ignition key
to on ( not start !!!) the check engine light will display a
code 12 which is one flash followed by two flashes.
this code will be flashed three times ..followed by the
trouble code stored in your car's computer.
what ever the code is it will be flashed three times.
have a paper and pencil ready and write down the
code .

code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
please remember that if you have the computer key installed
in the alcl and you start the engine ( you will ruin the engine's computer
)
only put the ignition to on (not to start)
If you should get a check engine soon display.. you can use
the above procedure and codes to buy the right part
or at the very least to keep from getting taken for a ride
and be made to pay hight prices for some inexpensive
module that you could have installed yourself.
You never ask a barber if you need a haircut ..
so you have to be on guard they will see you comming
a mile away.
If your engine displays a trouble code ... your engine will
go into limp mode ..it will still run but very poorly.
you might be able to reset the computer if it will not start
( just to get home ) by disconnecting both battery cables
and re-installing them ...this is not recommended ..but if
you are stranded it might help unitl you get your car home
or to a repair shop..good luck

1985 TO 1991:

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.

ECM CODES 1992 TO 1993:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.

CODES 1994 TO 1996:

DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.
_________________you really can,t be effectively at playing mr-fix-it with out the correct tools

especially on the more modern cars that are computer controlled, the days of effectively tuning by ear and vacuum gauge and engine sound went out with carbs
you need a few basic tools, now the list will vary, but you can,t get by by guessing, you neet to know and test now that sensors and CPUs control engine function
heres some basic tools

be sure to get the specific manuals your car and EFI system and ignition system,require FIRST

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4047

while it appears to be expensive, it saves you a good deal of money in the long run compared to dealing with the local chevy dealers mechanics, and makes diagnostics far faster, I bought this for the shop and it seems to be a good investment, since between a dealers diagnostics and swapping parts that don,t need changing you could easily spend close to that on just a few problems getting sorted out
youll also want a few basic diagnostic tools

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4417

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=6688

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=2597

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=8108

and a book or two

http://www.amazon.com/gp/product/0837608...ce&n=283155

http://www.amazon.com/gp/product/0879387...ce&n=283155

http://www.amazon.com/gp/product/0760304...ce&n=283155

in no time youll be the area wizz kid on chevy injection diagnostics

typical 1986 tuned port corvette engine

This is from http://shbox.com/

A fuel pressure test gauge can be bought at your local auto supply for ~$35. Attach it to the schrader valve that is on the fuel rail. Schrader valve location on 1994-1997

Normal pressure when the engine is not running and lines have been pressurized is 41-47 psi. This same pressure should be observed at wide open throttle (WOT). WOT can be simulated by removing the vacuum hose to the regulator at idle. At idle (because of the effect of the vacuum to the regulator) pressure will be less than what you observe with the vacuum line off. There may be anything from a 3 to 10 psi difference. NOTE: any indication of fuel in the vacuum line to the regulator, means the regulator is leaking and should be replaced. Check the line for fuel or the smell of fuel.
To fully determine that you don't have a pressure drop off during actual WOT situations, you should tape the gauge to your windshield and take it for a test run. This will tell you if the pump can meet actual fuel flow demands at pressure and not just at a simulated WOT condition (as when removing the vacuum to the regulator).
When you have a gauge connected and the pressure looks initially good and then bleeds off quickly when you shut the engine off, you can do a couple of tests to help you figure out where the pressure loss is.
What the factory manual says to temporarily install, is a set of "fuel line shut off adapters" (probably something the normal guy is not going to have available). You remove the fuel lines from the rail and connect these valves in between. This lets you shut off either side of the lines for testing.
You can do the same thing by pinching the flexible lines to shut them off, but risk breaking them. You might be able to do it (your risk) by using a needle nose vise grips and putting some scrap hose as cushions on the jaws. Then use that to clamp off the line just enough to seal it. Obviously, this is not the best way to shut off the lines and could result in breakage. Heat and age can make the hoses brittle. If you don't want to risk it, don't. It's just a suggestion.
You can use the fuel pump prime connector for pressurizing the system (jumper 12v to it to run the pump).
Watch your gauge as you jumper the prime connector. When you have good pressure remove the jumper and clamp off (or use shut off valve) the fuel supply line (3/8 pipe). If pressure holds, you have a leak on the feed line somewhere before it gets to the clamp (or shut off valve) or at the check ball in the pump. If it still goes down, release your clamp (or open shut off valve). Pressurize the system again, then remove the jumper and this time clamp (or shut off) the return line (5/16 line). If pressure holds, then the regulator is faulty. If pressure does not hold, you need to locate leaky injector(s). If you can't tell a leaky injector from reading the plugs, you can look and see if injectors are leaking by removing the fuel rail screws and pull the rail and all the injectors up, so you can see under them. Leave them over the injector ports. Pressurized the system and look under the injectors to see if any are dripping.

grumpyvette · Nov 29, 2008

Re: C4 sensor info
theres two oil pressure sensors located near the drivers side of the distributor base on the early TPI engines
http://garage.grumpysperformance.co...start-right-back-up-and-run.10739/#post-46893

http://garage.grumpysperformance.co...-corvette-intake-air-temperature-sensor.4819/

yes thats a rather common sensor to fail in a 20 plus year old corvette.
https://www.howacarworks.com/accessories/how-an-oil-pressure-guage-works

the gauge circuit works by reading OHMS resistance.
Basically a bad sender that is open would make the gauge peg.
When there is no oil pressure it is grounded.
Which is why unplugging it may have made no difference
some early c4 vettes have the gauge and oil pressure switch on an adapter near the distributor base into the block,
low oil pressure or a defective oil pressure sensor will cut off your ignition on many cars as a safety feature, the typical sensor and switch is located near the distributor base on the rear of the block.

most oil pressure and fuel pressure gauges now are electric and use a sensor and wires to transmit the sensor data to the gauge , the last thing you want is a broken line allowing fuel or oil under pressure to pass through the fire wall, in fact most racing rules forbid that oilder manual type of gauge use.

If your manual oil pressure gauge is stuck in one position ,check to verify the indicator needle is not bent, and you might also want to try spraying some carb cleaner solvent into the tube feeding oil pressure into the gauge then repeatedly applying high air pressure from your compressor,intermittently, and repeatedly, and removing the air pressure to cycle the solvent fluid in the tube to allow it to work its way up too the gauge to dissolve any sludge, in many case the tube has a fitting on the back of the gauge that can be temporarily disconnected so you can use solvent and air pressure to check the tube is clear and get easy access too the gauge internals.
obviously if the tubes blocked it needs to be cleared or replaced, if the gauge is defective, its probably cheaper to replace than repair

How to Set Minimum Idle on your C4

--------------------------------------------------------------------------------
the oil pressure switch might be defective, if the fuel pump won,t run, even if its new
and at $11-$35 Id just swap it out if your concerned

http://www.ecklers.com/product.asp?pf_i ... ept_id=153

http://www.ecklers.com/product.asp?pf_i ... ept_id=153

theres a good deal of good and useful advise, in this thread but Id point out the
sensor(s) next to the distributor, base ,could be a cause of a problem, because occasionally one of these starts acting up intermittently causing the fuel pump or ECM to stop working,or the VATS system, or the FUEL SUPPLY SYSTEM.

if you hear the fuel pump pressurize the fuel rails but the engine only starts than stalls, or fails to start, its frequently the fault of a defective oil pressure sensor

low oil pressure or a defective oil pressure sensor will cut off your ignition

both these sensors, located near the base of the distributor on the block, are known to fail & leak,oil at times, especially the smaller one with two blade connectors
the single terminal sensor runs the oil gauge the dual connector runs the fuel pump ONCE theres about 5 psi of oil pressure but they do fail and they do leak oil when they fail and both are commonly located near the distributor

How to Adjust your Early C4 TPS and Idle Speed -- 1 of 1
Date Published: 2001-10-01

Submitter's Name: Lars Grimsrud
Email Address: lars.grimsrud@lmco.com

How to Adjust your Early C4 TPS and Idle Speed by Lars Grimsrud SVE Automotive Restoration Musclecar, Collector & Exotic Auto Repair & Restoration Broomfield, CO
Rev. New 6-15-00
This tech paper will discuss the procedure for correct adjustment of the Minimum Idle Speed and for adjustment of the Throttle Position Switch (TPS) on the early C4 Corvette TPI systems.

These steps apply specifically to the 1985 model year, and in general to other years. Later model years do not have adjustable TPS's. General Idle speed and off-idle throttle response on the early TPI systems is determined by correct adjustment of the minimum idle speed screw combined with a correct setting of the TPS.

I've seen many of these cars that have had their idle speed corrected by well-intentioned mechanics and owners by simply screwing the minimum idle speed screw in a few turns. This really messes up the settings, and will not make your car perform properly. Doing a correct setup of the TPS is one of the easiest ways to make your car feel and respond better. To maximize the benefit of this procedure, I recommend that you first remove your Throttle Body (TB), disassemble it (it's incredibly easy, there are a total of about 5 pieces in it), clean the TB up really good with some spray carb cleaner, and put it back together.

A nice clean TB will really put an edge on the performance improvement you will get by doing this procedure. The Service Manual has instructions for doing these operations, but the directions are scattered through several sections of the Manual.

Here is the complete, step-by-step process for doing this (not including TB rebuild). All specs and steps are taken directly from the Manual (all 3 different sections), and this process is absolutely correct.

Tools & Equipment You will need the following tools and equipment:
1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears.
2. A good digital voltmeter that will read voltages less than 1 volt.
3. A paper clip.
4. A small screwdriver.

Procedure
There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC).

Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.

You will also be playing with the diagnostic connector under the dash. Remove the cover (if it's still in place). Bend your paper clip into a U shape. You will be playing with the two top right hand terminals (A and B) in the connector.
First step is to set the minimum idle speed. If nobody has messed with this on your car before, the set screw will be covered by a pressed-in plug. It's located on the driver's side of the TB. Remove this plug if it's there.
With the IAC connected and the ignition OFF, stick the paper clip into the diagnostic connector from A to B. This grounds the diagnostic lead.
Turn the ignition to the ON position without starting the engine. Wait 30 seconds.
Now, with the ignition still in the ON position, disconnect the IAC connector at the IAC.
Remove the paper clip from the diagnostic connector.
Start the engine and allow it to reach normal operating temperature. The idle speed will probably be really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.
If your car is an automatic, set the parking brake and put the transmission in DRIVE. If your car is a manual, leave it in neutral. Ã‚Â· Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.
Shut off the engine and re-connect the IAC. That's it for idle speed.

Now on to the TPS.

There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.

Turn the ignition to the ON position without starting the engine.
Loosen the TPS Torx adjustment screws. Ã‚Â· Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.
Measure the voltage between the two top TPS wires.
Adjust the TPS by rotating its position until you get a reading of .54 volts.
Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.
Turn the ignition OFF. You are now in perfect adjustment on idle speed and TPS output.

Start the engine. It may take a few seconds for the car to catch on to its new settings.

this infos bound to be helpful at times
Sensor Locations

Sensor
Location

Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

Sensor Outputs:

Sensor
Measured Value

Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.
grumpyvette is online now Report Post IP Edit/Delete Message

http://garage.grumpysperformance.co...p-after-running-out-of-fuel.11309/#post-51444

grumpyvette · Nov 29, 2008

Re: C4 sensor info

IAC and TPS Adjustment
FROM THIRDGEN.org

http://www.thirdgen.org/tpimod2

Tom Keliher Mar 31 2006 - 8:07pm
Idle Air Control
Tools needed:

Torx bit # T-20
Paper Clip
Small Punch

Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.

Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

Throttle Position Switch (TPS)
Tools needed:

Digital Volt-Ohm-Meter (VOM)
Jumper Wires (make your own)
Auto Xray Scanner (if available) will eliminate the need for VOM and jumper wires.

Turn on ignition, but don't start the engine.

With a scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.075Volts

With VOM and jumper wires: disconnect the connector from the TPS. Using your jumper wires, make a connection allowing some room for the VOM terminals to contact the jumper leads and read the TPS voltage.

If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and driveability problems.

After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.

every mechanic needs an ANALOG multi meter for testing capacitors with a micro farad scale, AND a DIGITAL MULTI METER

http://forum.grumpysperformance.com/viewtopic.php?f=36&t=63&p=3403&hilit=vats#p3403

Injector pulse

I’m new to the site and would like to know if anyone has come to know the transistor that is used to switch the injectors in the ECM? I have a 1989 and lost pulse signal, tested ECM and it is not switching. The number on this part is 499587, it also has Y9P38747 on it, as of yet I am not able to...

garage.grumpysperformance.com

use of a shop manual and multi meter can be very helpful

grumpyvette · Jan 15, 2009

Re: C4 sensor info

tired of your C4 corvette running hot?
vacume diagrams and other useful info

http://www.autozone.com/addVehicleId,11 ... 528008fdc3

http://www.ecklers.com/product.asp?pf_i ... pt_id=1127

http://www.ecklers.com/product.asp?pf_i ... pt_id=1126

http://www.autoenginuity.com/

http://vettaid.com/default.aspx?cid=RECSOtkYNdo=

1963SS said:
How about this? Pins "A" and "B" are the upper right two pins on your ALDL viewed from the driver's seat. Paper clip works great.

Pin "B" is the diagnostic enable pin and pin "A" is ground. Grounding pin "B" to enable the diagnostic readout of the ECM/PCM.

To recover the codes, short pins "A" and "B" together using a small section of electrical wire or paper clip.

With the ignition turned OFF, short pins "A" and "B" on the ALDL.

Turn IGN ON (but not to RUN).

The "Check Engine" light (early C4s) or "SYS" light (later C4s) will flash a Code 12 (a single flash followed by two flashes) and will repeat three times (Flash (pause) Flash Flash (long pause), Flash (pause) Flash Flash (long pause), Flash (pause) Flash Flash (long pause).

Code 12 is a delimiter or marker code to show where the error code string begins and ends.

After the three Code 12 flashes, you will either get an error code (or codes) or you will get another string of Code 12 flashes if there are no trouble codes stored.

All codes are repeated three times with a long pause between each code group (36 or Flash Flash Flash pause followed by six flashes, repeated three times, folowed by a long pause with any additional codes stored then flashed).

The "Check Engine/System" light on with engine running means the condition(s) are currently present. If the light is not on during RUN operation, the limits were exceeded at some point in time and the event was recorded in memory, but the reading has since returned to the normal operating range.

Remember to remove the shorting device from the connector after you have read the codes.

Clearing the Codes

To clear the codes from memory, remove the negative battery cable for a minimum of 10 seconds.

Disconnecting the battery will clear all stored codes and and any stored memory (radio button presets, clock, trip odometer, average gas mileage memory, power seats). Your ECM/PCM computer will also have to relearn timing/mixture/exhaust emissions.

Make absolutely certain the ignition key is turned OFF. If you connect the battery with the ignition switch ON, you can destroy the ECM/PCM module.

grumpyvette · Jun 23, 2009

Re: C4 sensor and relay/switch locations and info

http://www.corvettebuyers.com/c4vettes/ ... mation.htm
EMISSION COMPONENT LOCATIONS

Sensor

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

you really need a scan tool of some sort to work on corvettes

1982-1993 Corvette Computer OBD I Code Scanner Reader

Define service problems on your 1982-1993 Corvette by reading trouble codes.

www.corvettecentral.com

ZR15s OBD2 Code Reader with 3.5 In. Display and Active Test/FIXASSIST

Amazing deals on this Zr15S Active Test Obd2 Code Reader at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

http://www.gosale.com/4924033/actron-cp ... 2godkQqywQ

at about $140 its certainly affordable, but its basically a deluxe code reader

http://garage.grumpysperformance.co...p-after-running-out-of-fuel.11309/#post-51444

http://stores.channeladvisor.com/Summit ... ms/BBE-ATU

this seems to be a better deal, at $199

http://www.etoolcart.com/autoxray-scann ... x6000.aspx

this is what I bought,(about $400) but mines several years old and theres even better ones out there now

The factory shop manuals are available from Helm, Inc. The following links will take you to the correct location for all years of C4 Vettes. OWNING A FACTORY SHOP MANUAL ,AND A FEW BASIC DIAGNOSTIC TOOLS IS MANDATORY IF YOU INTEND TO ISOLATE AND REPAIR A CORVETTE

1984

1984 Factory Service Manual

1985
1985 Factory Service Manual

1986

1986 Factory Service Manual

1987

1987 Factory Service Manual

1988

1988 Factory Service Manual

1989

1989 Factory Service Manual

1990 (Separate ZR-1 (LT5) Manuals are sometimes listed from 1990 thru 1994)

1990 Factory Service Manual

1991

1991 Factory Service Manual

1992

1992 Factory Service Manual

1993

1993 Factory Service Manual

1994

1994 Factory Service Manual

1995 (No separate ZR-1 Service Manual)

1995 Factory Service Manual

1996

1996 Factory Service Manual

grumpyvette · Jun 3, 2010

Re: C4 sensor and relay/switch locations and info

CHECK ALL YOUR FUSES and electrical connections WITH A MULTI METER, but don,t assume you know what the problem is, let the facts lead you to the answers
be aware that not all engine "MISSES" or "ticking sounds " that you might be dealing with or trying to correct, are an electrical or a fuel delivery or pressure issue, your problem might be a mechanical issue like a vacuum leak, from a busted hose,or loose gasket,a burnt valve, loose or worn timing chain,badly adjusted valves, broken or loose harmonic damper, loose flex plate, or torque converter bolt, busted valve spring, burnt or defective rocker, loose or worn valve guide, or a dozen other issues so try to logically isolate it to a cylinder or system, electrical,valve train, fuel delivery, exhaust , ignition ,etc.

http://www.harborfreight.com/5-in-1-dig ... 98674.html
having a wide assortment of different multi meter test leads available is a huge benefit while testing
the clip test leads that test thru a wires insulation without much damage are a big help

THE DIAGRAM ABOVE HAS THE CORRECT WIRE COLORS

#
http://shbox.com/1/4th_gen_tech2.html
this looks interesting with a discount coupon its discounted to about $169.99 until 4/30/18 plus $49.99 for a two year 100% warranty

http://garage.grumpysperformance.co...pro-scanner-harbor-freight-zurich-zr13.14833/

https://www.hotrodhandbooks.com.au/eBooks/TPI/TPI On Line-03-1.html
if you purchase a ZR13 auto code scanner, from HF,
you need this info
DOWN-LOAD AND PRINT IT OUT!

https://manuals.harborfreight.com/manuals/63000-63999/Q63806.pdf

https://manuals.harborfreight.com/manuals/63000-63999/63806.pdf

https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore,f,EAFeatured+Weight,f,Sale+Rank,f&q=zr13

Last edited: Oct 14, 2018

Cooling System Operation and Testing

http://www.aa1car.com/library/electric_cooling_fan.htm

http://www.aa1car.com/library/air_temp_sensors.htm

http://www.aa1car.com/library/cooling_f ... oblems.htm

http://www.aa1car.com/library/coolant_sensors.htm

http://www.aa1car.com/library/overheat.htm

Electric cooling fans attached to the radiator keep the LT1 from overheating when there is little or no air passing through the radiator core (car going very slow or stopped and engine running). It is normal for the temps on the gauge to go up to the middle or past middle of the gauge before the fans kick on. The middle of the gauge is in the range of 210Âº - 220Âº. With factory programming, the PCM will command low speed fans (or primary fan) "ON" at 226Âº and "OFF" at 221Âº and high speed fans (or secondary fan) "ON" at 235Âº and "OFF" at 230Âº. The fans should come on before it gets to any part of the red zone. (see "dual fan configuration" below about primary and secondary fans)
The f-body LT1 uses a 180Â° thermostat as stock.

The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in fuel calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running.

The gauge gets it's information from a sensor that is in the driver's side head. Inaccurate gauge readings can be from this sensor or it's wiring (the wire burned on a header pipe is common). The temp that the PCM sees can be monitored with a scan tool and compared to the gauge reading. They should be close, but don't expect them to be "perfectly" synchronized.

The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed.

Fans will also come on when the SES lamp comes on. The PCM does this when certain (most) DTCs are detected to protect the engine from a situation where it may overheat.

There are two versions of the dual fan configuration:

# 1993-1994 - Primary and Secondary fans that operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed.
These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood.

# In late 1994 and into 1995, there was a change to low and high speed fans. When initially commanded on, both fans will come on at a low speed. When the high speed temp threshold is met, they both bump up to high speed. A three relay architecture is used for this fan version (seen in the fuse/relay panel). By adding a third relay, low speed can be achieved by running the power to the fans in series. This way, each fan does not get full voltage and runs at a slower speed. High speed happens when the relays switch to provide full voltage to both fans. Low speed is less noisy and should result in greater fan longevity. High speed is not always needed.

2 Relay System PCM Commanded Fan Operation PCM Wire Color Grounded Fan Operation Relay Operated
#1 #2 #3
Primary@226Âº Drk Grn @A11 Primary (LH) fan full speed X - n/a
Secondary@235Âº Drk Blu @A10 Secondary (RH) fan full speed X X n/a
3 Relay System Low Speed@226Âº Drk Grn @A11 Low Speed (both fans) X - -
High Speed@235Âº Drk Blu @A10 High Speed (both fans) X X X
For both fans to operate in either system, both relay leads must be grounded. Grounding only the Drk Blu wire will result in only the RH fan operating at high speed.

Here are some fairly simple things to check for various complaints:

~Fans are not operational at any time~

# Check fan fuses in the underhood fuse/relay panel
# Check fan relays (same location). Aside from getting out any electrical equipment to test the relay, you can swap it with another one (such as the fog lamp relay) and test for function. See if the relay works for the fog lamps and/or the swapped-in relay makes your fans work. Nearly all the relays in the panel are the same, except for maybe the ABS relay.
# You can jumper two pins on the DLC that should cause the fans to come on. 1993-1994 cars with the 12 pin DLC can jumper pins A and B. On a 1993, that is the same way that you would retrieve trouble codes from the ecm. The 1994 won't give you any codes, but the fans will engage. 1995-1997 uses pins 5 and 6 on the 16 pin DLC to initiate what is called "field service enable mode". That will cause the fans to come on and operate most sensors for sanity checking. After placing the jumper on the correct pins, turn the key to ON (don't start). If the fans work after jumpering the DLC, your PCM is capable of operating the fans and all fan wiring/relays should be ok.
# Deeper problems can be solved through testing and using the wiring schematic.

~Fans don't come on except when the a/c or SES is on~

~Temp gauge continues to rise with no automatic fan operation~

# With a scan tool, check to see what temp the PCM is seeing from the sensor in the water pump. Make sure you are aware of the temps the fans come on (stated in the beginning of this article). If the temp it sees is incorrectly low, it won't know to turn the fans on. Another possibility is that the temp is really ok, but the gauge is reading wrong. That is why you need to use the scan tool to see and compare the readings. Info on testing wiring and sensor can be found here.
# If that looks ok, then your PCM may have issues. You could always try resetting the PCM by pulling the PCM BAT fuse for about 30 seconds.

Testing the ECT (Engine Temperature) Sensors and Connections

ECT Temperature vs. Resistance Values

ÂºC ÂºF Ohms
100 212 177
90 194 241
80 176 332
70 158 467
60 140 667
50 122 973
45 113 1188
40 104 1459
35 95 1802
30 86 2238
25 77 2796
20 68 3520
15 59 4450
10 50 5670
5 41 7280
0 32 9420
-5 23 12300
-10 14 16180
-15 5 21450
-20 -4 28680
-30 -22 52700
-40 -40 100700

Use a Digital Volt Meter (DVM) set to ohms to measure resistance. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM. Most modern DVMs will do, but your old analog meter can damage the PCM. It is also a good idea to get a " reference" from the meter you are working with. With the DVM on the ohms scale, touch the two meter leads together and note the ohm reading. It may not always be perfectly zero, but may be within a tenth or two. Now when you take an ohm reading, you will know what the meter will show when there is really no resistance.

* The sensor in the head has only one terminal. This sensor is for the temperature indicator on the dashboard. Place one test lead on the sensor terminal and the other on a known good ground. Compare the reading to the table. If your car is cold from sitting overnight, the reading should be close to ambient temperature.
* The sensor in the water pump has two terminals. This sensor is for the temperature input to the PCM. Place a test lead on each of the sensor terminals to take the reading. (When reading resistance, it does not matter which lead goes to which terminal)

If the sensor seems to be ok, you may also need to test at the harness connector for proper lead conditions. Use your test meter set on the dc voltage scale to do this. You will need the key in the RUN position, but don't have to start the car.

* For the one lead connector at the head, place the red test lead on the connector terminal and the black test lead to a known good ground. With the key ON, you should read battery voltage (+12vdc or close to it). You can also ground the lead and see if the gauge in the car deflects to full hot.
o If you get no voltage, switch the meter to ohms to see if the lead is grounded.
o No voltage or no ground mean that the lead is open.
o If the gauge is at full hot all the tme, the lead is grounded back toward the gauge. It could be possible for the lead to be pinched and grounded toward the gauge and broken and open back toward the sensor (like in the case of the wire getting caught somewhere during some major engine work). Physically tracing the wire from the sensor into the harness should locate the problem.
* The two lead connector at the water pump has a black (ground) lead and a PCM +5vdc power lead (probably yellow). Place the black meter test lead to black connector lead and the red meter test lead to the other connector lead (yellow on my 1995). You should read +5vdc because this is monitoring voltage being supplied from the PCM.
* If you get no reading:
o Test the yellow lead by placing the DVM red lead on it and the DVM black lead to ground. A +5vdc reading will indicate the lead is ok.
+ If you get no voltage, switch the meter to ohms to see if the lead is grounded.
+ No voltage or no ground mean that the lead is open.
o You can test the black connector lead by using the ohms scale on the DVM. Place the DVM black lead to ground. Place the DVM red lead to the black lead of the connector. If the lead is ok, you will get an ohm reading close to zero. If you get no reading or a very high one, the lead is open or partially open.
* OBD-I DTCs 14 and 15 or OBD-II DTCs P0117 and P0118 are typically associated with problems the PCM sees with the sensors or circuits.

Footnote: If you ever have to test the IAT, it operates the same as the two lead coolant sensor. The same temp vs. resistance table above is applicable to the IAT, as well as the +5vdc lead and ground wire at the harness connector.

grumpyvette · Sep 9, 2010

Re: C4 sensor and relay/switch locations and info

oxygen sensor related info
http://www.chevythunder.com/Flow chart index.htm

http://www.chevythunder.com/fuel%20inje ... pg%20B.htm

viewtopic.php?f=32&t=1401

http://www.chevythunder.com/fuel injection elect. pg B.htm

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.co...-auto-elecrtrical-connectors.3105/#post-68805

http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/

viewtopic.php?f=44&t=987&p=2395&hilit=intermitant#p2395

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
it helps if you understand that oxygen sensors do not measure your true fuel air ratio,entering the engine, but instead measure the remaining oxygen content of the burnt exhaust gases,and there are both narrow and wide band sensors

there have always been 2 on those.... the right side is not as visible...

these are delco part numbers.... at a dealer they will have a different part number for them to use.. but it will have the AFS numbers on the bag also...

SENSOR ASM,OXY
Part Number: 213-3857
Product Notes:
[Oxygen Sensor]; Universal Upstream
Per Vehicle: 2; Years: 1984-1991
Vehicle List

SENSOR ASM,EXH OXY
Part Number: AFS21
Product Notes:
[Heated Oxygen Sensor (Position 1)]; In exh manifold/crossover ; Type #21
Per Vehicle: 2; Years: 1988-1991
Vehicle List
CORVETTE(10) 1982-1992
1992 V8-350ci 5.7L F/I Vin P
1991 V8-350ci 5.7L F/I Vin 8
1990 V8-350ci 5.7L F/I Vin 8
1989 V8-350ci 5.7L F/I Vin 8
1988 V8-350ci 5.7L F/I Vin 8
1987 V8-350ci 5.7L F/I Vin 8
1986 V8-350ci 5.7L F/I Vin 8
1985 V8-350ci 5.7L F/I Vin 8
1984 V8-350ci 5.7L F/I Vin 8
1982 V8-350ci 5.7L F/I Vin 8
CORVETTE LT1(1) 1993-1993
1993 V8-350ci 5.7L F/I Vin P

SENSOR ASM,EXH OXY
Part Number: AFS22
Product Notes:
[Heated Oxygen Sensor (Position 1)]; In exh manifold/crossover ; Type #21
Per Vehicle: 2; Years: 1988-1991

CORVETTE(14) 1980-1992
1992 V8-350ci 5.7L F/I Vin P
1991 V8-350ci 5.7L F/I Vin 8
1990 V8-350ci 5.7L F/I Vin 8
1989 V8-350ci 5.7L F/I Vin 8
1988 V8-350ci 5.7L F/I Vin 8
1987 V8-350ci 5.7L F/I Vin 8
1986 V8-350ci 5.7L F/I Vin 8
1985 V8-350ci 5.7L F/I Vin 8
1984 V8-350ci 5.7L F/I Vin 8
1982 V8-350ci 5.7L F/I Vin 8
1981 V8-350ci 5.7L 4 BBL Vin 6
1980 V8-305ci 5.0L 4 BBL Vin H
1980 V8-350ci 5.7L 4 BBL Vin 6
1980 V8-350ci 5.7L 4 BBL Vin 8
CORVETTE LT1(1) 1993-1993

http://www.corvettebuyers.com/c4vettes/ ... mation.htm

C4 Sensor Information

http://www.aa1car.com/library/air_temp_sensors.htm

The C4 Corvette makes use of numerous sensors that feed information to the ECM/PCM (Electronic Control Module/Powertrain Control Module) and to the instruments on the dashboard.

Even if the sensor is operated by vacuum or pressure, the output is converted into an electrical signal for processing by the ECM.

Most faulty sensors will cause a trouble code to be set (resulting in a 'Check Engine/SYS ' Light) and also alter the performance of the automobile.

When troubleshooting the reason for the code, the normal approach is to go straight to the sensor and assume that it is faulty.

While this may be the normal practice, you are strongly cautioned that it is seldom the sensor but rather a connector, a power problem or a grounding issue that is actually causing the problem.

Or, the sensor may simply be doing it's job and reporting an occurrence that is at variance with what is allowed or expected by the ECM/PCM.

In any event, because the sensor really is the easiest thing to check, the following information is provided to assist you in determining if the device is operating properly.

You will need a D-VOM (Digital Volt-Ohm Meter) to check the items below. It should have at least a 10 megohms per volt rating---something that will be shown in the specifications.

For those sensors listed below that have ohms listed as the measurement item, disconnect the negative battery terminal and then the sensor harness connector and measure the sensor's terminals.

For voltage measurements, you can obtain test harnesses from any of the Corvette specialty catalog houses.

Before beginning your efforts, print the ECM codes page along with this page so you can cross reference the code information with the sensor information.

Sensor Outputs:
If your having issues with a temp gauge not reading correctly the first thing you need to find out is that you need to know the correct sensors ohms resistance value for a given heat level and what the gauge is expecting to see.,if the sensors providing the gauge with the wrong resistance the gauge will show the wrong temp indication, heres a typical sensor
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
but its far from rare to find a sensor that has wildly different ohms values, at different temperatures, depending on the manufacturer and intended application, or to have a defective sensor that only randomly changes resistance,
an INFRARED TEMP GUN AND A MULTI METER CAN BE USED TO VERIFY SENSOR OUTPUT

If you buy a MULTI METER< CODE SCANNER AND SHOP MANUAL YOU CAN GET MUCH BETTER AT FINDING AND FIXING PROBLEMS IF YOU then try disconnecting a few sensors and USE THE SCANNER TOO see if the scanner indicates the problem correctly
while you do the testing on the disconnected sensors take notes,and also use a multi meter to test voltage and ohms resistance on connectors and sensors,having listed the results on correctly working and disconnected sensors, and having been listed what the voltage and resistance and trouble codes that result from that testing will come in very handy later as a reference

RELATED LINKS
viewtopic.php?f=80&t=728&p=1025&hilit=sensors+camaro#p1025

viewtopic.php?f=32&t=2697&p=29270&hilit=multi+meter#p29270

viewtopic.php?f=50&t=609&p=810&hilit=multi+meter#p810

viewtopic.php?f=32&t=1401&p=3104&hilit=multi+meter#p3104

http://www.eficonnection.com/eficonnection/default.aspx

viewtopic.php?f=50&t=609&p=1298&hilit=multi+meter#p1298

viewtopic.php?f=44&t=469&p=7163&hilit=multi+meter#p7163

viewtopic.php?f=50&t=3110&p=8302&hilit=multi+meter#p8302

viewtopic.php?f=36&t=317&p=13210&hilit=multi+meter#p13210

viewtopic.php?f=87&t=5492&p=16502&hilit=multi+meter#p16502

having a few basic meters,gauges etc. helps

MULTI METER

http://www.testequipmentdepot.com/extech/thermometers-and-humidity-meters/infrared-thermometers/high-temperature-infrared-thermometer-58to1832f-50to1-laser-pointer-42545.htm?utm_source=bing&utm_medium=cpc&utm_campaign=NEXT - Bing Shopping - Extech&utm_term=1100200223789&utm_content=All Extech Products
having the correct tool to verify the engines operational temps would be helpful
INFRARED TEMP GUN

TIMING LIGHT

COMPRESSION GAUGE

PRESSURE/VACUUM GAUGE

Sensor

Measured Value

Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. (lower sensor above oil filter) 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.

some early c4 vettes have the gauge and oil pressure switch on an adapter near the distributor base into the block

Oil Pressure Sender/Switch. (top sensor in picture above) 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.

Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.

low coolant sensor
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.

MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
does anyone have a link or detailed info, hopefully with a clear diagram, showing the location of OXYGEN SENSORS in a 1996 corvette?
Yes IM fully aware theres One in front of each catalytic converter , and One behind each catalytic converter but ID love a clear diagram or detailed pictures showing the location
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

KNOCK SENSOR
Sensor Locations

Sensor
keep in mind theres DOZENS OF DIFFERENT CHEVY TEMP SENSORS, for OIL AND COOLANT AND AIR, SO BE SURE YOU SELECT THE ONE DESIGNED TO MATCH YOUR GAUGE AND APPLICATION

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front[/color].[/size][/b]
http://garage.grumpysperformance.co...at-manifold-air-temp-sensor.10349/#post-42530
mass air flow sensors and air filters

http://www.youtube.com/watch?v=sSuL58YE ... ure=relmfu

http://www.knfilters.com/MAF/massair.htm

http://www.knfilters.com/MAF/2MAFSensorVideo.htm

http://www.knfilters.com/MAF/3MAFSensorVideo.htm

http://www.knfilters.com/MAF/4MAFSensorVideo.htm

viewtopic.php?f=50&t=6134

http://www.corvettephotographs.com/c4vettes/maf.htm

http://garage.grumpysperformance.co...at-manifold-air-temp-sensor.10349/#post-42530
"Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

IF YOU CLEAN THE MASS AIR FLOW SENSOR YOU MUST USE THE CORRECT PRODUCT
many throttle body and carburetor spray cleaners used will leave a film that won,t burn off and will cause error codes or the wrong sensor readings
A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

Theory of Operation

As the air travels past the heated wire en-route to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

MAF Operating Conditions

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

MAF Problems

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

MAF Mods

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter."

http://www.mamotorworks.com/corvette-c4 ... 6-893.html
http://content.mamotorworks.com/pdf/601096.pdf

you will want to isolate and verify every systems functioning correctly, before proceeding to the next test.
lets assume everything's in need of tweaking until checked, if you don,t have a SHOP MANUAL, timing light, multi meter,vacuum gauge and code reader, your working at a disadvantage
each bit of info you verify provides you with clues to the cause of any problems or adds or eliminates potential areas to look into

(1)pull the plugs and post VERY clear pictures with the cylinder locations labeled .
Id suggest swapping to new AC or NGK plugs gapped at .045 as a start point.
(2)measure the battery voltage with a multi meter both before starting and at idle
(3)measure EACH individual ignition wire OHMS, end to end and post results
(4) whats the BACK PRESSURE on the exhaust at idle and 3000rpm?
(5)VERIFY the firing order, TDC and IGNITION ADVANCE CURVE
(6)clean the throttle body and IAC, reset the TPS
(7)whats your fuel pressure at idle and at 3000rpm
what does each fuel injector read in resistance?
is the fuel pressure steady?
is there fuel in any vacuum lines?
(are you sure the timings correct and youve verified TDC on the dampers CORRECT?
(8) have you verified theres no vacuum leaks?
(9) have you recently adjusted valves? you should at least check them
(10) do you have an IR temp gun?, what does each header read next to the head?

http://autospeed.com/cms/A_110895/artic ... larArticle

http://tpiparts.net/90_92_speed_density_sensors/

http://tpiparts.net/85_89_maf_sensors/

what codes are still there?

heres a couple related threads with links and sub-links that will provide you a great deal of related and useful info related too cooling your corvette
http://garage.grumpysperformance.com/index.php?threads/cooling-off-that-c4-corvette.3954/
http://garage.grumpysperformance.co...t-of-logic-to-locate-a-problems-source.14297/
http://garage.grumpysperformance.co...-air-conditioner-on-cooling.12232/#post-59597
http://garage.grumpysperformance.co...e-out-intermittent-fan-issue.9229/#post-33215
http://garage.grumpysperformance.co...es-got-me-scratching-my-head.7499/#post-25445
http://garage.grumpysperformance.com/index.php?threads/cooling-issue.13389/
http://garage.grumpysperformance.com/index.php?threads/1995-corvette-fan-motor-quit-working.10559/
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-69239
http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-66935

bob · Nov 6, 2011

Re: C4 and camaro sensor and relay/switch locations and inf

http://www.classictruckshop.com/clubs/e ... /relay.htm

http://www.the12volt.com/relays/relays.asp

http://www.offroaders.com/info/tech-cor ... wiring.htm

http://www.cadvision.com/blanchas/54pontiac/relay.html

Electrical - Automotive Relays

I purchased some new industrial automotive style relays for dirt cheap and immediately ran into a strange problem with the starting circuit. I determined that the relays were missing a bleed down resistor. The bleed down resistor is across the coil and it is used to help bleed down the magnetic field after you've stopped applying +12V to the coil. Automotive relays have the bleed down resistor already built in. You can read about the problem here in the starter circuit page.

3 different styles of automotive relays

A relay is a magnetically controlled switch. They are composed of two circuits: the coil and the contacts. When +12 volts is applied to the coil, a magnetic field is generated that pulls in the contacts. The contacts are the switch portion of the relay. The contacts are rated for how many amps of current they can handle. Automotive relays are typically rated for 30 amps at 12 Vdc. For example of current consumption, one halogen headlight draws about 4 amps on hi beam.

Relays are used to control high current devices such as horns, headlights, brake lights, etc.. I don't like to run high currents through 50 year old switches in the dash, so I use them to control the relay coils which only need about 1/10 the current of the contacts and let the relay contacts control the high current draw devices.

Relay wiring code

Relay pigtail socket

Automotive relay pins are labelled with numbers which indicate what their purpose is and the relay pigtail has a standard color code as follow:

Coil

85: Ground - Black wire
86: +12V - White wire

NOTE: I found that in half of my pigtails, the black and white wires were reversed! It shouldn't make a difference as the coil is not polarized.

Contacts

30: Common - Blue wire
87: Normally Open (NO) - Yellow wire
87a: Normally Closed (NC) - Red wire

grumpyvette · Dec 13, 2011

Re: C4 and camaro sensor and relay/switch locations and inf

http://garage.grumpysperformance.co...e-out-intermittent-fan-issue.9229/#post-33215

http://www.megamanual.com/v22manual/mwire.htm

heres a link with a bunch of useful sensor related info

grumpyvette · Aug 11, 2012

Re: C4 and camaro sensor and relay/switch locations and inf

http://www.professionalequipment.com/ex ... ermometer/
Wide temperature range from -58 to 1832Â°F (-50 to 1000Â°C)
any time that your dealing with a potential temperature issue or a trouble issue where , knowing the exact temperature vs what a gauge might say, it helps to have a handy and accurate infrared temp gun handy to locate and confirm heat, levels.
I FOUND THIS POSTED ON A DIFFERENT SITE

The "paperclip method" - it does more than you think, even on '96 cars!
I am posting this to clear some things up about the "paperclip" trick as it applies to later model C4's ('94-'96), and I just want to make sure nobody is in the dark about all the various features of their car's built-in diagnostic mode. I will show that it does a lot more than display codes (it's got a menu!), and I will show you what the "SYS" message means, and I also hope to clear up some major misinformation.

Specifically, there have been numerous rumors that the 1996 cars have no diagnostic mode. You can enter the '96 diagnostic mode, but the rumors say it's only a holdover from previous years and that everything shown on the screen is garbage. This is false. The 1996 cars DO have an elaborate and functional diagnostic mode, with only one major change.

Our cars have numerous computers (it calls them "modules") networked together, one of which is the PCM, which controls the engine. The root of the rumors lies in the fact that in '96, new laws mandated the PCM's protocol to change to OBD-II, which used a standardized four-digit numbering scheme for "check engine" codes, which is too big to fit on the LCD. Rather than find some other way to display that many digits, GM decided to say screw it and deleted the functions that read/clear PCM codes from the diagnostic mode. The PCM simply no longer shows up at all among the modules listed.

They forgot to mention this little tidbit in the service manual, which confused a lot of people into thinking that the whole CCM chapter does not apply to '96 cars, but other than that one detail, it does. GM did not change any of the functions involving other modules (CCM, EBTCM, etc), nor did those functions get corrupted by the switch to OBD-II; they all still show up and function correctly. Thus the majority of the diagnostic mode's power is still there in '96. I know because I checked.

-----Using diagnostic mode-----

To enter the diagnostic mode, you simply ground the diagnostic pin on your car's diagnostic connector (located near the driver's knees). Various DLC connectors were used throughout the C4's life, all with different pinouts; on '94-'96 cars, you connect the fourth pin from the left in each of the two rows of pins to one another, with a paperclip or some other conductor.

When you turn the ignition to "run," you will now be in diagnostic mode, which uses the LCD screen and the DIC (driver information center) buttons for input and output. You may start and drive the car while in diagnostic mode; in fact, the car has to be running for some of the functions to be meaningful. The only disadvantage is you will not be able to see your normal gauges while in this mode since the LCD screen will be in use.

When you start diagnostic mode, the LCD will show you any codes stored in the car's various computers. In '96, Module 1 is the CCM (main/dash computer), 4 is the PCM (engine computer, doesn't show up in '96), 7 is the RTD (computer-controlled shock absorbers, if you've got them), 9 is the EBTCM (antilock brake and traction computer), and A is the DERM (air bag computer). These are cycled through one at a time, with dashes indicating the end of codes for that module. A "C" prefix means the code is currently active, meaning that the relevant parameters are out of range right now; an "H" means the code has been stored in history but is not currently active.

Unlike the car's other electronic systems, such as PCM, ABS, air bags, etc., there is no specific "CCM" lamp to indicate a malfunction when one is present. Instead, the CCM flashes the word "SYS" three times every once in a while on the LCD whenever there are active CCM codes present. If the code thrown is one that involves only the security system, the "SECURITY" lamp will illuminate instead, or they will both flash together if it involves the Fuel Enable Data Stream.

Upon entering diagnostic mode, as mentioned, you will first see a listing of diagnostic codes for each module. Afterwards, you will enter the menu (or you can press any information center buttons to skip to the menu). Did you know there was a menu? I didn't, until I read the FSM.

You'll know you're in the menu when you see the number "1.0". The first digit, before the decimal point, refers to which module you are talking to at the moment, as numbered above. The second digit indicates the menu item. Item .0 means that computer is awaiting instructions. Item .1 displays any codes for that module and .7 clears them. This applies to all of the car's computers/modules. Note that any non-CCM codes will always show up with the "H" as in history, since the CCM does not know whether or not they are currently active.

The CCM has additional options on top of these; .2 and .3 let you cycle through the CCM's stored data and inputs, respectively, and option .4 lets you toggle each of its outputs manually (this part is fun).

To navigate the menu items, use the "gauges" and "trip odo" button. To navigate to the next or previous module, hold down the "fuel" or "trip" button for a second. To select a menu item, press "ENG MET."

One thing that I recommend doing at this point, is see if you have any EBTCM codes stored (module 9 in '96), and then delete them. You will hear the brake pressure modulator valves near the EBTCM click as it resets, and you might suddenly feel that your brakes feel and work much better than before. This was the case for me; I had a lateral accelerometer code, as well as a code from back when my Opti died making the tachometer go crazy. Neither code has come back since I cleared them, meaning that the presence of codes alone was enough to severely effect how my brake functions.

Now for the fun part: The CCM data, input, and outputs. These are options .2, .3, and .4 in the CCM module menu, respectively. After selecting any of these, press "eng met" to go to the next value and "fuel info" to go to the previous. The selections are:

Display CCM Data (Mode 1.2):
01 - Fuel Level (Gallons, tenths)
02 - Dimming Potentiometer
03 - Ambient Light Sensor
04 - Rear Defogger Timer
05 - Vehicle Speed
06 - Pass-Key
07 - Ignition Voltage
08 - Switched Voltage
09 - Cluster dimming
10 - LCD backlight dimming
11 - Radio & Climate dimming
12 - LED dimming
13 & 14 - Vehicle configuration
15 - Oil monitor count
16 - CCM version

Display CCM input status (Mode 1.3):

1 - PassKey fuel
2 - English/metric status
3 - Door key switch
4 - Right Door ajar
5 - Left door ajar
6 - key in ignition but in "off" or "acc" position
7 - hatch ajar
8 - Power door unlock
9 - Power door lock
10 - Parking lights
11 - Rear defogger input (car must be running)
12 - Seat belt switch
13 - High beam switch
14 - Low oil level switch

These values are either "1" or "0," and when toggled, the new value will be appended on to the old value (01 means it was 0 but is now 1).

Cycle CCM Outputs (Mode 1.4):

Selecting these options will manually activate the lights and sounds the CCM produces.

1 - Change oil light
2 - Check gauges indicator
3 - Fasten seatbelt indicator
4 - Security lamp
5 - High beam indicator
6 & 7 - chimes
8 - LCD blanking
9 - Defogger relay
10 - Courtesy lamp
11 - Low oil lamp
12 - Theft relay
13 - DAB relay
14 - door ajar light
15 - Horns (This will actually beep the horns, watch out!)

So there you have it; you can now dazzle and impress your friends with your car's diagnostic features, as well as test any of the circuits and systems in the interior. Please correct any factual errors I have made in this post, and if you know of any information that would be useful to add to this thread, so as to make it a centralized source for information about the late model CCM, let me know.

Here's the fan diagram which also shows the 3 fuses involved in the fan circuit.

There are 3 relays and two modes of operation when the fans run.

Both fans run at slow speed when the PCM grounds pin A11 Dark Green wire which energizes Relay #1.

Both fans run at high speed when the PCM grounds pin A11 Dark Green wire and pin A10 Dark Blue wire. (All 3 relays are energized).

I've never tried this but If you ground Pin 5 to Pin 6 on the DLC (Data Link Connector) above the drivers right knee and then turn the ignition ON, the 3 Fan relays should energize and both fans should operate at high speed.

[01|02|03|04|05|06|07|08]
[09|10|11|12|13|14|15|16]

BTW FAULTY GROUNDS, IN MANY CARS AND ESPECIALLY NEWER CORVETTES CAUSE MANY ELECTRICAL ISSUES SO IF YOU HAVE INTERMITTENT ELECTRICAL ISSUES CHECK THEM CAREFULLY

http://www.jegs.com/p/Equus/Equus-8000-Series-Gauges/1532060/10002/-1

it might help to understand why the manufacturers selected BATCH FIRE VS individually timed by cylinder injection controls to begin with, that that was basically because back in the early 1980s computer processing speeds were a BAD JOKE compared to the potential computer processing speeds currently available.the early corvettes like my 1985 came with a 160 baud processor speed, this was so slow that it took almost a full second to respond to sensor data,and make the next change required, making use of things like dry nitrous injection that in theory would rely on the engine sensing the overly lean fuel/air ratio a massive increase in oxygen to fuel ratio a sure way to burn pistons, simply because the early cpu processor speed was hopelessly slow. batch fire allowed the computer to control 4 injectors with a single control pulse ,effectively reducing the required processor speed by 75%
some of the early tpi injection intakes like the 1985 came with a 9th cold start injector whos only real function is to act as a choke and richen the fuel air ratio during cold engine starts
the function of the cold start injector on the 1985 tpi is to provide extra fuel, acting like a carb choke richening the fuel air ratio, if you just plug off the fuel rail and intake and remove the 9th injector it will still run OK just like a carburetor, without a choke will once its up to operating temperature, but it will be a P.I.T.A. to start on cool mornings and ALWAYS take a bit longer to start up, as would a carb engine without a choke because EFI doesn,t have the accelerator pump function where you can remove or bye-pass the symptoms by flooring the carb several times , to get the accelerator pump shot to richen the fuel air ratio.
but what you can do is upgrade the absurdly slow 160 baud processor this meant the computer control responding to sensor input,could ad or remove fuel only a couple times a second the CPU has to a more current version which controls ALL the injectors and RICHENS all the pulse durations to all the injectors under cold start conditions, thus eliminating the need for the 9th injector or installing its feed or connectors, but obviously the rear of the drivers side fuel rail needs to be plugged if the 9th injector feed is removes as will the injector mount hole in the intake manifold if its been removed
data is sent at 8192 baud by 1989, or 51 TIMES FASTER, and by todays standards the 1989 processor speeds a joke itself.as current speeds are hundreds of times faster, allowing individual cylinders to be tuned independently hundreds of times a second
viewtopic.php?f=32&t=2825

http://garage.grumpysperformance.com/index.php?threads/testing-1985-89-m-a-f-sensor.1475/#post-43635

http://garage.grumpysperformance.co...g-your-tpi-maf-and-cpu-links.2825/#post-56790

85-89 MAF TPI Systems

Below is a list of all the needed sensors to install a MAF TPI setup, and each of their functions.

Mass Air Flow (MAF) Sensor: This sensor is responsible for measuring air volume and density. It is located in the air duct, before the throttle body. All of the air that the engine consumes must first pass through the MAF sensor. At the center of the MAF, is a very thin wire whose resistance increases as it goes up in temperature. A constant voltage is applied to this wire. Air being drawn through the MAF has the effect of cooling this wire, which lowers its resistance, and increases current. As you might suspect, the more air is drawn through the MAF sensor, the greater the current flow. It is important to note that hot dry air is less dense and has less mass than cool moist air. As a result, hot dry air will cool the wire less than cool moist air.

A circuit mounted on the MAF sensor serves to convert the current flow into a variable frequency square wave on 1985 models, which is sent to the ecm. MAF units from 86-89 models output a simple analog signal instead of using frequency modulation like the 1985 units. The ecm will calculate the amount of fuel needed depending on the signal from the MAF sensor. It is very important that there are no air leaks (from a ripped air duct for example) between the MAF and the throttle body.
Oxygen Sensor: Responsible for determining the amount of oxygen in the exhaust manifold. Depending on how much oxygen is in the exhaust, the ecm can determine whether or not the air/fuel mixture is rich or lean. The signal sent to the ecm by the ecm varies between 0.0 and 1.0 volts. An ideal mixture (also known as a Stoichiometric mixture) of 14.7:1 is represented by .450 volts. If the oxygen sensor voltage is below .450, then the air/fuel mixture is lean. Anything over .450 means the mixture is rich. Since the sensor is essentially just a switching device, it will be fluctuating alot between lean and rich. This is normal, and an indication that the sensor is in working properly.

Keep in mind however that oxygen sensors (except wideband oxygen sensors), are not very accurate below or above .450 volts. Exhaust gas temperature will affect the oxygen sensor reading as well. The sensor will not read properly until exhaust gas temperature reaches approximately 600 degrees Farenheit. If you have headers installed, it is a good idea to use a heated oxygen sensor (3 wire) instead of the usual single wire sensor. Headers usually place the oxygen sensor further down the exhaust stream, where exhaust temperatures are cooler. A heated oxygen sensor will heat itself, allowing a more reliable sensor reading than a single wire sensor. If you have factory exhaust manifolds, then the single wire sensor is adequate.

Oxygen sensors are a regular maintenance item, and should be replaced every 30,000 miles. When an oxygen sensor goes bad, it tends to read lean, and will not fluctuate very much. The ecm will attempt to correct this false lean condition by richening the mixture. This will cause poor driveability, and high gas consumption.
Knock Sensor: Also known as detonation sensor, it is responsible for sensing spark knock. Basically, thats when the fuel mixture ignites before the spark plug fires. The piston is moving upwards as this premature combustion takes place. Since fuel is used to cool down the combustion chamber, a lean condition causes the temperature to rise, and ignites the fuel mixture prematurely. This is very abusive on the engine internals, and reduces the life of any engine. The more powerful the engine, the greater the potential for damage. Detonation can be cause by a variety of things. One of the more common causes on TPI retrofits where prom changes have been made to the fuel or spark tables is a lean condition. It isn't always loud enough to be heard, so just because you don't hear any pinging, doesn't mean its not happening.

Detonation will cause a vibration to travel through the engine block. The sensor listens for this vibration at a certain frequency, and sends a signal to the ecm when the frequency is heard. This frequency is different depending on engine size. To prevent possible engine damage, the spark timing needs to be retarded when detonation is present. The sensor itself does not pull the timing back however. The ecm is in charge of retarding the timing, and will do so according to a series of settings inside the prom. The knock sensor is located on the passenger side of the engine block on factory applications. It can however be relocated to the driver side of the block if needed (header clearance for example). They are different depending not only on the size of the engine, but also the ecm being used. It is important that the correct sensor is used to avoid problems. Although it is possible to run the car without one, I strongly suggest against this. I have had customers come to me looking for a $45 knock sensor after spending several hundred dollars and an extra month of work rebuilding a blown engine due to detonation.
Throttle Position Sensor (TPS): Responsible for reporting to the ecm the position of the throttle blades. The ecm will receive a signal which can vary from 0.0 to 5.0 volts. At idle, the TPS should be read .54 volts (factory specification) unless it has been set to a different value inside the prom. If it does not read .54 volts and the idle TPS voltage setting has not been modified in the prom, then it should be adjusted. Under full throttle, it should output close to 5.0 volts. Throughout its range of motion, the voltage should climb steadily, without any jumps or falls. If it is not steady or has some fluctuations as it is moved through its range of motion, it should be replaced. This sensor is located on the passenger side of the throttle body.

Coolant Temperature Sensor (CTS): This is basically a thermistor (means that it changes resistance with temperature) that supplies the ecm with the temperature of the engine coolant. This temperature reading is used for several important functions. The most notable is that the ecm adds extra fuel to an engine when its cold, and as the engine warms up, the extra fuel is reduced. This sensor mounts at the front of the intake manifold. The chart below shows the approximate resistance for this sensor in relation to temperature.

the later 1992-96 corvette lt1 used a MAT SENSOR

Intake Air Temperature Sensor (IAT): This sensor is also a thermistor (means that it changes resistance with temperature) that supplies the ecm with a temperature reading of the air being drawn into the engine. It is the same as the coolant temperature sensor on 86-92 models. The 1985 intake air temperature sensor used a different connector and cannot be used as a coolant temperature sensor because it had an exposed bulb. This sensor mounts underneath the plenum. The chart above shows the approximate resistance for this sensor in relation to temperature.

Idle Air Control (IAC) Valve: Although this is technically not a sensor at all, people often treat it as one. It is responsible for regulating the amount of airflow being admitted into the engine to adjust engine speed, particularly at idle and deceleration. The ecm controls the IAC at its discretion. The IAC works by moving a cone shaped pintle, which can extend and retract as needed to admit or block off incoming air. The valve moves the pintle in "steps". These steps are numbered and range from 0 to 160. A properly adjust throttle body should be idling when warm between 15-25 steps.

The IAC is used under a variety of conditions, not only at idle speed. The valve mounts on the bottom coolant plate of the throttle body.

Vehicle Speed Sensor (VSS): This is responsible for providing the ECM with the vehicle speed. It can be located either at the tailshaft of the transmission, or behind the speedometer on cars with a cable driven speedometer. It sends a 2k ppm (pulse per mile) square wave signal, and is needed for a variety of functions. It is absolutely critical for the ecm's learn mode, timing retard, emissions, torque converter lockup (automatic lockup transmissions only), idle speed control, and to avoid stalling on deceleration. It is possible to run without one. However, your car will NOT be street legal if you are required to retain emissions equipment, the ecm will not control the torque converter lockup, the ecm will not retard timing if you run into detonation, and it is possible to run into stalling /idle speed issues. In addition, the ecm will not adjust the fuel table properly as you drive (known as its "learning ability"). If the ecm does not know the vehicle speed it is assumed to be 0 mph.

If you still insist on not running a vss, I very highly suggest that the minimum vehicle speed for timing retard be brought down to 0 mph in the prom. The factory setting is 2 or 3 mph. If you don't bring this value down, and you do not run a vss, the ecm will NOT retard your timing under detonation.

grumpyvette · Aug 23, 2012

Re: C4 and camaro sensor and relay/switch locations and inf

http://www.aa1car.com/library/oxygen_se ... ations.htm

http://sethirdgen.org/HO2S.htm

http://www.ngksparkplugs.com/techinfo/o ... country=US

http://tech.corvettecentral.com/2007/01 ... en-sensor/

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.

Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
does anyone have a link or detailed info, hopefully with a clear diagram, showing the location of OXYGEN SENSORS in a 1996 corvette?
Yes IM fully aware theres One in front of each catalytic converter , and One behind each catalytic converter but ID love a clear diagram or detailed pictures showing the location

knowing your true compression ratio would help, as would knowing your converter stall speed, exhaust back pressure at peak rpms and plenum vacume reading at peak rpms and your ignition timing and advance curve.
posting clear pictures of your spark plugs labeled to match the cylinders would also be useful, as would any info on jets and power valves, accelerator pump cams , and fuel pressure etc. If you were local we could work out the testing and details far easier, things like voltage, and exhaust,back pressure, fuel pressure get over looked but they can be great indicators

http://tpiparts.net/emissions

Emissions Devices

Disclaimer: The information contained within this article is intended for educational purposes only. It may be illegal to remove, modify, or tamper with any emissions device on your vehicle, depending on the state in which you live. Please check your local rules and regulations to ensure that you abide by them.

Before we discuss how these systems operate, I would like to comment on a general misconception associated with fuel injection in general. I have heard on numerous occassions that fuel injection in general is too complicated and restrictive due to emissions devices. In reality, the problem lies with people assuming that the emissions components are somehow required as part of the whole fuel injection platform, and that these devices pose a significant restriction in performance. Just because you are running a fuel injection system, does not mean you will have emissions devices. In addition, having emissions equipment does not prevent someone from running whatever engine modifications they want. The loss in power from these emission devices is quite small.

As many of you already know, Tuned Port Injection engines were factory installed on vehicles that were required to be emissions compliant. To ensure that emissions requirements were met, GM used several devices to lower emissions output. Basically, these can be broken down into three main systems : EGR, A.I.R., and EECS. None of these are absolutely necessary to run a Tuned Port Injection intake, but may be legally necessary if you want to be street legal in the state where you live.

Exhaust Gas Recirculation System (EGR)

The sole purpose of the EGR system is to reduce the formation of Oxides of Nitrogen (NOx). These are formed when the temperature in the combustion chamber reaches very high levels. To avoid this situation, the EGR system is used to lower combustion chamber temperatures by admitting small amounts of exhaust gas back into the combustion chamber. As you can imagine, exhaust gas does not burn, and does not help the combustion process. If the EGR system would admit exhaust gas into the combustion chamber at idle, it would cause a rough idle, or stalling. As a result, EGR does not allow exhaust gas into the chamber at idle (nor at wide open throttle, more on that later...). To accomplish this, there has to be some way of controlling EGR flow.

The way this is accomplished is actually quite simple. First of all, there is a round, flying saucer - looking part that mounts on the intake manifold. This is called the EGR valve. There is an opening in the intake manifold from the cylinder head that allows exhaust gas to move up to the valve. When vacuum is applied to the valve, it allows the exhaust gases to pass. To control when the valve receives vacuum, an EGR solenoid is used. This part mounts on the passenger side near the back of the intake manifold. It has a vacuum line which supples ported manifold vacuum, and another vacuum line running to the EGR valve. When the ECM requests EGR to be ON, it sends a signal the the EGR solenoid, which then allows vacuum to be applied to the EGR valve. When the ECM wishes EGR to be off, the solenoid will cease to apply vacuum to the EGR valve.

The ECM will turn on the EGR solenoid by grounding it. It does this via pulse width modulation (PWM). This means that the ECM will turn on and off the solenoid many times a second. Just how many times this occurs will affect the amount of vacuum applied to the EGR valve, and therefore the amount of exhaust gas admitted into the combustion chamber. During the time that EGR is requested by the ECM, fuel output and spark advance are also altered. More timing is added, and the fuel mixture is leaned a bit.

During WOT (wide open throttle), the ECM shuts down EGR. Since EGR will play no role whatsoever under WOT, it will not impede the engine's ability to generate horsepower.

How does the ECM know if there is a problem with the EGR system? Well, the answer depends on what year TPI setup you have. If you have an 85-89 setup, then there will be a single wire that goes to the base of the EGR valve. This is basically a temperature switch. When the ECM requests EGR, it will check this wire to see if there is a change in temperature. If no change is detected, the ECM will think there is a problem with the system, and will throw a code 32. Most of the time, the problem is the temperature switch that is bad. However, you should first check for vacuum leaks, check that all vacuum lines are properly routed, check the harness connector at the EGR solenoid with a voltmeter, and make sure that the EGR passages are not clogged with deposits.

The 90-92 TPI setups did not use a temperature switch on the EGR base. Instead, the ECM monitors the MAP voltage to determine if an EGR request was successful or not. When EGR is turned on, engine vacuum will lower a little. The ECM will throw a code 32 if it suspects that the EGR request was not successful.

So what would someone gain by disabling EGR? Just about the only thing would be less parts under the hood. Basically, removing EGR gives you more space (although not much). To correctly disable EGR from your vehicle, you MUST at the very least, disable it in the prom. This is done by setting the minimum temperature to enable EGR to 151 degrees Celsius (maximum allowable temperature), and setting the minimum vehicle speed to enable EGR to 255 mph (maximum allowable speed). Since the engine will never reach either of these conditions, EGR will never be requested by the ECM. Since EGR will never be requested, it does not matter if you leave the EGR system all installed in its original place, or if you remove it from the car. If you decide to remove it, you will need an EGR block off plate to cover the hole in the intake manifold.

If you simply remove the EGR system from the car, but do not disable it in the ECM, you will run into significant problems. You will likely run into detonation, the engine will run very poorly, lack power, and will probably run on the hot side as well. In addition, you will get a code 32 before running very long. If you recall from before, the ECM alters fuel and spark advance when it thinks EGR should be on. If no EGR flow is possible because you removed it, you will have a lean condition which will be further aggravated by advanced timing.

I have not had a chance to discuss A.I.R or EECS (canister purge). I will finish the article as soon as I have some spare time, but I wanted to post the EGR section for the moment atleast.

related info, yes I know there,s a ton of reading in links and sub links but its also a great deal of useful info

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=181&p=215&hilit=broken+rocker+stud#p215

http://forum.grumpysperformance.com...=6237&p=19552&hilit=broken+rocker+stud#p19552

http://forum.grumpysperformance.com...=4949&p=13698&hilit=broken+rocker+stud#p13698

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=9478&p=34812&hilit=shop+manual#p34812

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=168

http://forum.grumpysperformance.com...3&p=35176&hilit=just+running+correctly#p35176

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=9687&p=36006&hilit=just+running#p36006

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=596

http://forum.grumpysperformance.com...808&p=2957&hilit=running+right+tracking#p2957

http://forum.grumpysperformance.com/viewtopic.php?f=55&t=9570&p=35327&hilit=just+running#p35327

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=4683&p=34611&hilit=just+running#p34611

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=34392&hilit=just+running#p34392

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=661

grumpyvette · Jun 14, 2014

Re: C4 and camaro sensor and relay/switch locations and inf

jktucker92 said:
There are books written out there that can give you the advantages / disadvantages of each system, but I'll try to keep it brief. In order to run as efficient as possible, you need to mix fuel and air at a specific mass ratio. 14.7:1 is the Stoichiometric ratio that is ideal, but richer mixtures can provide more power. With a MAF sensor, you measure the mass of the air flowing in the intake, which makes the calculation of how much fuel simple and accurate. The problem is the MAF sensors are more expensive than a simple pressure and speed sensor, especially early on. Also, the MAF sensors can be restrictive when you want to increase performance, so they are often removed in high performance applications. A speed density system uses the speed of the engine, manifold pressure, and temperature to calculate the mass of the air flowing into the intake and into the cylinder. This is pretty accurate, but not as accurate as a MAF sensor. As a result, the engines generally are tuned to run a little richer than the MAF systems to avoid damaging the engine by running too lean all the time.
Whether an engine is batch or sequential injected is a different, but related topic. In order to have sequential injection, the engine must be port injected, and the injector fires on each cylinder as each valve is opened. Batch systems can fire all the injectors on each revolution, or half one one revolution and the other half on the next. As it comes out of the injector, it's a fine mist, and the longer it is in the manifold, the more that mist becomes larger droplets, which burn less efficiently. Port injected systems are better than throttle body systems because their injectors are close to the ports and the fuel stays in the fine mist better.
The most efficient system is a MAF sequential injected system, which is why all new vehicles are MAF sequential injected systems.

other related info
viewtopic.php?f=32&t=1401

http://garage.grumpysperformance.com/index.php?threads/so-you-failed-emmision-testing.3522/

http://garage.grumpysperformance.com/index.php?threads/digital-dash-swap-questions.3399/#post-26865

the search feature, is always an option here, on this site, but to save time , look at the sub links in these threads, to find sources for replacement electrical connectors, and NAPA can frequently ORDER replacement connectors for repairs at about 3- 5 times the cost youll find them at else ware, but at times getting the part the next day beats waiting a week so the price may be justified. if its a connector thats likely to break frequently buy extras, and have them handy

grumpyvette · May 12, 2015

Grumpy · Sep 23, 2015

Im always amazed at the guys that don,t
STOP AND GRAB A FEW TOOLS AND THE SHOP MANUAL.
break out the shop manual ,
THINK LOGICALLY ISOLATE AND TEST, CHECK YOUR FUSES AND FOR LOOSE ELECTRICAL GROUNDS AND CONNECTIONS TO SENSORS!

GET out the multi meter, and a fuel pressure gage,
and do a few quick tests for loose electrical connections, look for vacuum leaks and consistent fuel pressure on the fuel rails
and verify the alternator voltage is at or above 13.5 volts,
when things don,t run correctly and the guys that don,t
pull the trouble codes, they are skipping a step that may waste hours
obviously the basics always apply ,
its CRITICAL to keep the trans fluid clean and ideally changed about every 70K miles and use of a auxiliary cooler that keeps the fluid temp under about 170F is going to extend service life a good deal longer

you need to think carefully, don,t assume anything.
TEST AND VERIFY EVERY COMPONENT AND SENSOR FUNCTION!
Id suggest pulling trouble codes and verifying the basics of engine function,
are you actually getting spark at ALL the plugs?
are you getting injector pulse from the injector wire harness, do you have fuel pressure?
have you been checking the too verify your actually getting fuel out of the injectors,into the cylinders?
are all the fuses in the panel good?
have you verified that your alternator produces 13.5 plus volts,
that your getting spark at all the spark plugs ,have you verified the spark plugs are actually arcing and not fuel fouled?
your getting compression in all cylinders, all the rockers move, as the engine rotates?
ALL the sensors are fully functional,
your getting at least 10 psi of oil pressure as the engine spins while its trying to start,
you need to see the fuel pressure is consistently at 38-42 psi.
you need to verify the fuel filter and fuel pressure regulator and return line are functioning as designed.
verify all the electrical grounds are good,
and you use a noid tester to verify your getting the injector pulse.
what most people fail to do is test and verify, you can,t assume anything.
youll want too verify, youve got no plenum or runner vacuum leaks, and the catalytic converters are NOT restricting exhaust flow, theres no excessive exhaust system back pressure.
just because the injectors have pressure in the fuel rail, and get a pulse does NOT insure fuel flow thru them,
and having fuel rail pressure does not insure ITS GOOD fuel,
it can be tainted with water or rust particles in the fuel,
preventing fuel atomizing in the cylinders.
clogged catalytic converters can easily cause the engine to fail to flow air,
checking the plenum vacuum and exhaust back pressure and reading the exhaust fuel/air ratio,
use of an infrared temp gun, to verify cylinder exhaust temps are reasonably equal and a multi meter to set the TPS sensor and verify the ignition wire resistance will help.
simple stuff like verifying the firing order that you just know is correct (which may not be , so VERIFY IT) get over looked
and testing the coil and oxygen sensors and temp sensors sure helps.
After you verify theres consistent strong electrical spark at the spark plugs when your trying to start the engine and fuel pressure is consistent at the fuel rails,and your getting at least 7-8 psi of oil pressure,
IF you suspect a fuel delivery related issue, a good long spray of starter fluid into the throttle body and trying to start the engine with that extra fuel source may prove informative, if it trys to start with the extra fuel in the plenum but failed to start without it, its a good indicator the injectors are plugged or defective

if you suspect water in the fuel pull the inside of the shrader valve

with a valve tool, and slip 12 feet of braid re-enforced 5/16" pvc hose over the valve ,

clamp it with a screw clamp

on the valve so theres less chance of a fuel leak, and let the fuel pump push a 1/2 gallon of fuel out of the fuel rail into a clear glass container on the floor , allow it to settle for 15 minures and look for water to settle out of the fuel.

https://www.summitracing.com/parts/anm-cp7838

and rev the engine a few times and watch the fuel pressure it should in theory remain in the 38 psi-42 psi range for most TPI and TUNED PORT efi

IF you want to upgrade the current one wire oxygen sensor on the earlier c4 corvettes to a later more effective three wire oxygen heated sensor...

For wiring I found this, I also used as a guide for what one to buy:
http://sethirdgen.org/HO2S.htm
http://www.rockauto.com/en/catalog/...l+v8,1041398,emission,oxygen+(o2)+sensor,5132
3-wire Heated Oxygen Sensor: 25176708
3-wire Weatherpack Connector: 12126012

You will notice the sensor has two white wires and one black. The white wires can be interchanged, polarity does not matter. One must go to a good clean ground, either on the body or the engine block, and the other must go to a 12V switched ignition source (Power w/ the key in the "RUN" position). Many people tap into the MAF power wires if you have a MAF sensor, but any "hot" wire in RUN only will work. It can't be HOT all the time, or you will drain your battery.
The black wire goes to the stock PURPLE wire that originally went to your one-wire Oxygen sensor. This is the signal wire to the ECM.

Click to expand...

having a few basic meters,gauges etc.
IT sure helps too have basic tools, when isolating issues

https://www.the12volt.com/relays/relaydiagrams.asp (read)
without testing you simply guessing
GET A FUEL PRESSURE GAUGE AND MEASURE DON,T GUESS
how can you possibly set up your fuel system unless you know the pressure and flow rates required and what currently exist's

as always it helps to have a shop manual for your year and model car, then I'd suggest, you get out your multi meter and verify the alternator is putting out about 14 volts while the engine runs,pull the trouble codes with a code reader, then check the electrical grounds and fuses as a first step, in isolating the problems source

reading these links will be helpful
yes I know it will take some time and effort to isolate and test
but its the only 100% sure route to finding and fixing your problem,
don,t get over whelmed,
simply break the problem down to testing each basic sub system,
test each related sensor and electrical component and electrical sensor and connection.
some reading on the threads posted below, a bit of logic and deductive reasoning, and a multi meter and a shop manual will go a long way toward finding and fixing the problem.

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

this is the most consistently accurate I.R temp gun I've used for testing[/img]

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN
you always need a base line to start from, on a corvette.
a logical step by step approach and keeping accurate notes helps.
youll NEED a multi meter, a shop manual
and a timing light and fuel pressure gauge at a minimum,
set and verify your ignition timing, pull trouble codes,set your tps and iac,, then check for vacuum leaks on the lines and intake,then get out your multi meter and verify all the sensors, chances are good a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful
http://www.helminc.com/helm
http://www.factoryrepairmanuals.com...ice-manual-2-volume-set-original-shop-repair/

your working at a huge dis-advantage if you don,t have a factory shop manual for your specific year car, and basic tools like a multi-meter, and vacuum /pressure gauge

http://www.harborfreight.com/fuel-injection-pump-tester-92699.html

http://www.harborfreight.com/5-in-1-dig ... 98674.html

viewtopic.php?f=50&t=3110&p=12074&hilit=multi+meter#p12074
MULTI METER

INFRARED TEMP GUN

TIMING LIGHT

COMPRESSION GAUGE

PRESSURE/VACUUM GAUGE

Here's some flow figures, right off the manufactures sites in many cases. Keep in mind the concept of the chains weakest link. It does ABSOLUTELY no good to match a base or runners on a TPI intake that flows 250cfm if the other part flows 200cfm. You'll still only flow 200cfm. The HOLLEY STEALTH RAM FLOWS at 275cfm out of the box,(minor port clean-up work) and can easily reach 300cfm with minor port work. The stock TPI has a hard time flowing 230cfm even with minor port work. Look here. Most of this info is right off the Accel, Holley, Edelbrock, and TPIS sites. Add a little math and the results become much clearer!!!

Intake......runner length .... port in...... out
Stock GM Base----- 6.375"------------- 1.47"------- 1.96x1.20
TPIS base------------6.125"------------- 1.75"------- 2.09x1.28
Accel base-----------6.125"------------- 1.75"---------2.09x1.28
Holley base--------- 6.000" ------------ 2.30â€-------- 1.90x1.23 (2.337 sq inches)

Runners
Stock TPI-------- 7.250"------1.470" round(1.70 sq inches)
SLP -------------- 6.625"------1.600" round (2.01 sq inches)
Accel LTR------- 6.625"------1.615" round (2.05 sq inches)
TPiS-------------- 7.625"------1.660" round (2.168 sq inches)
Mini ram --------3.500â€
stock MRII with 1204 (AFR 195) ports, 58MM - 265 cfm
stock MRII with 1206 (AFR 220) ports, 58MM - 281 cfm
MRII clean-up, 1206 ports, 58MM - 292 cfm
MRII cut, weld, port, etc, 58MM - 321 cfm
LT1 ----------3.000â€

Runners (measured individually)
Stock........................................................................................................................................203.17 cfm
ACCEL.....................................................................................................................................242.02 cfm
Extrude/ACCEL........................................................................................................................275.83 cfm
Super Ram................................................................................................................................289.18 cfm
Intake manifold with 3/8 inch radiused inlet .............................................................................222.45 cfm
Holley stealth ram â€¦â€¦â€¦..........................................................................................................275.00 cfm

Stock intake manifold with runner
Stock.........................................................................................................................................198.72 cfm
ACCEL......................................................................................................................................213.52 cfm
Extrude/ACCEL.........................................................................................................................217.11 cfm
Super Ram.................................................................................................................................220.67 cfm
Holley stealth ram â€¦.................................................................................................................275.00 cfm
ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.....................................................251.51 cfm
ACCEL Hi-Flow intake manifold with runner Stock...................................................................215.83 cfm
ACCEL......................................................................................................................................232.53 cfm
Extrude/ACCEL.........................................................................................................................243.21 cfm
Super Ram.................................................................................................................................240.24 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.............................275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner.......................................266.94 cfm
Edelbrock Performer RPM manifold (Stock)...............................................................................286.51 cfm
Edelbrock Victor Jr....................................................................................................................275.24 cfm

Runner Length

Stock TPI manifold ...................8â€ ...............runners 11.25â€............... cylinder head 6â€.............total 25.25â€
Accel super ram manifold........ 8â€................runners 7.00â€............... cylinder head 6â€............ total 21.00â€
Holley stealth ram manifold .....6.26â€ ................................................. cylinder head 6â€............ total 12.26â€
Edelbrock performer RPM ...........................runners 6.00â€................ cylinder head 6â€............ total 12.00â€
Edelbrock Victor Jr .......................................runners 5.50â€................ cylinder head 6â€............ total 11.50â€

Now playing with the figure in the calculators below, what you'll find is that if your using a 350 size engine as a guide, the tpi runner length is ideal for peak tq 3427rpm and 2700-4000rpm for peak hp.

The Accel Super Ram is ideal for peak tq at 4032rpm and 3300rpm-4800rpm for peak hp.

Holley's Stealth Ram runner length is ideal at 4700 for peak tq and 5618rpm to 6282rpm for peak hp.

The TPIS Mini Ram and LT1 intakes are ideal for peak tq at about 5200rpm and 7244rpm to 8101rpm for peak hp.

By hp peak, in the above lists, I'M REFERRING TO THE RPM RANGE WHERE combination of cross sectional area MATCHED TO THE plenum to INTAKE valve distance WHERE THE internal AIRFLOW HARMONICS TEND TO INCREASE THE CYLINDER FILLING EFFICIENCY (WHERE THE INTAKE WILL TEND TO PULL THE MOST HP). Now KEEP FIRMLY IN MIND the engines tend to enter valve float and get close to engine red line by 6300-6700rpm depending on your combo. After running all the available combos, I've found a HOLLEY STEALTH RAM has been EXTREMELY EFFECTIVE on several engines tested. CURRENTLY THE STEALTH RAM SEEMS TO
BE THE CHOICE, ESPECIALLY IF MATCHED TO GOOD CYLINDER HEADS AND THE CORRECT
CAM.

bytor said:

Came across this info while doing some research and thought I'd share.

http://www.hobracing.com/tech/tpi_flow.asp
TPI Intakes and runners

The following airflow tests were performed on the University of Northwestern Ohio's SuperFlow SF600 Flow Bench. All CFM values are corrected for airflow at 28 inches of water. Injector flow rates are flowed at 43.5 PSI on an injector flow bench using test fluid with same density as gasoline.

AirFlow

Stock TPI/LT1 48mm Throttle Body w/o airfoil -- 783.0 cfm

Stock TPI/LT1 48mm Throttle Body w/ airfoil -- 821.9 cfm

TPI/LT1 52mm Throttle Body w/o airfoil -- 848.9 cfm

TPI/LT1 52mm Throttle Body w/ airfoil -- 898.8 cfm

Stock 98 Camaro 3800 II Throttle Body -- 554.3 cfm

Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm

Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm

Stock 87 GN 3.8L Turbo AC MAF sensor w/ screen -- 584.2 cfm

Stock 86 2.8L AC 5-wire MAF sensor w/ screen -- 576.2 cfm

Stock 96-up AC 3100 V6 MAF sensor w/ screen -- 616.4 cfm

Stock 96-up AC 3100 V6 MAF sensor w/o screen -- 670.7 cfm

Stock 94-up LT1 MAF Sensor w/o screen -- 719.0 cfm

Stock 85-87 Firebird TPI airbox mid piece -- 499.3 cfm

Stock 4.3/5.0/5.7 2bbl TBI complete -- 574.1 cfm (dry)

Stock 4.3/5.0/5.7 2bbl TBI w/o injectors -- 584.7 cfm

Stock 3800 vin L throttle body w/ screen -- 419.1 cfm

Stock 3800 vin L throttle body w/o screen -- 444.8 cfm

4bbl MPFI Holley Throttle Body -- 1287.6 cfm

Another source sent in these flow numbers

Flow and HP ratings for Throttle-bodies:

Flow (cfm) Max. NA HP
Stock 668 300
Stock w/airfoil 710 350
52MM w/airfoil 835 400
54MM (AS&M) 900 450
58MM 1050 500

TPI Intakes and runners flow rates

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm

the stock TPI has a hard time flowing 230cfm even with minor port work, look here
most of this info is right off the accel,holley,edelbrock, and TPIS sites, add a little math and the results become much clearer!!!

Intake....... length ....... port in -- out
Stock GM Base--- 6.375"------ 1.47"- 1.96x1.2
TPiS base------ -6.125"------ 1.75"- 2.09x1.28
Accel base----- -6.125"------ 1.75"- 2.09x1.28
Holley base------- 6” runner 2.3”- 1.9”x 1.23 (2.337 sq inches)
Runners
Stock TPI----- -- 7.250"------1.470" round(1.70 sq inchs)
SLP ----------- - 6.625"------1.600" round (2.01 sq inchs)
Accel LTR------- 6.625"------1.615" round (2.05 sq inchs)
TPiS----------- 7.625"------1.660" round (2.168 sq inchs)
Mini ram -----3.5”
LT1 ----------3”

Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet.............................222.45 cfm
Holley stealth ram ………..275cfm

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm
Holley stealth ram …..275cfm

ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.........251.51 cfm

ACCEL Hi-Flow intake manifold with runner
Stock....................215.83 cfm
ACCEL................232.53 cfm
Extrude/ACCEL....243.21 cfm
Super Ram............240.24 cfm

Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet ...............275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner ..............266.94 cfm
Edelbrock Performer RPM manifold (Stock)..........286.51 cfm
Edelbrock Victor Jr. ............275.24 cfm

HOLLEY STEALTH RAM
the HOLLEY STEALTH RAM FLOWS at 275cfm out of the box, and has the potential when matched to the correct heads and cam to totally out flow most other intakes available,can easily reach 300cfm with minor port work and costs much less
Stock…………………………… 275cfm
Ported…………………………..300cfm

Runner lengths
Stock tpi manifold 8” runners 11.25”, cylinder head 6” total 25.25”
Accel super ram manifold 8” runners 7” cylinder head 6” total 21”
Holley stealth ram manifold 6.26” ” cylinder head 6” total 12.26”
Edelbrock performer RPM runners 6” ” cylinder head 6” total 12”
Edelbrock vic jr , runner length 5.5” ” ” cylinder head 6” total 11.5”

Also interesting TPI mods. Not so sure I agree with the one on bumping up the initial timing.
http://www.hobracing.com/tech/tpi_mods.asp

read the links and sub links

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/

Click to expand...

bytor said:

http://garage.grumpysperformance.co...h-flicker-on-dash-and-radio.13593/#post-70202

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-69824

http://garage.grumpysperformance.co...u-need-to-know-setting-float-levels-etc.1115/

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/

http://garage.grumpysperformance.com/index.php?threads/1984-fuel-pressure.11776/#post-55675

http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.com/index.php?threads/replacing-a-c-4-fuel-pump.33/

http://garage.grumpysperformance.com/index.php?threads/c3-c4-corvette-vacuum-diagrams.1773/

http://garage.grumpysperformance.co...ckpressure-hurting-your-combo.495/#post-26600

http://garage.grumpysperformance.com/index.php?threads/what-kills-o2-sensors.3049/#post-51701

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477

Click to expand...

Grumpy · Oct 23, 2016

1985 to 1991 Computer Codes

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52: (1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.
1994 to 1996 DTC Computer Codes
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.

1992 to 1993 DTC Computer Codes

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.

1985 ECM Codes
Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52: (1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.
1982-1984 ECM Codes
Code #12: Normal System No Codes.
Code #13: Oxygen Sensor Circuit:
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low
Code #24: Vehicle Speed Sensor.
Code #33: Manifold Absolute Pressure Sensor Signal High.
Code #34: Manifold Absolute Pressure Sensor Signal Low
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control..
Code #44: Lean Exhaust Indication.
Code #45: Rich Exhaust Indication.
Code #51: PROM Error.
Code #55: Defective ECM.

The full range of human hearing WHEN WERE YOUNG extends from 20 to 20,000 hertz."
as we get older we very frequently LOOSE a percentage of that full audible range
(USUALLY ON BOTH ENDS OF THE SCALE)
ID also point out that some rolling tire noise, some wind noise,etc. also falls in that low hertz range and could easily mask or cover the detonation even if you could in theory hear it occur
(your average muscle car cab sound level reads at well over 80DB under hard acceleration)

most destructive detonation or KNOCK in an engine occurs at and audible range of 1/2 or LESS of the HERTZ RANGE of the LOWEST human HEARING RANGE THRESH HOLD for many adults
(notice on the chart that a 4.1" bore would generally have detonation or pinging at less than 60 hertz)
if your thinking youll hear an engine in detonation PING! youll have to wait until its well past the critical destructive range, thats one reason they developed accurate sensors

https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm

http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml

http://www.jandssafeguard.com/index.html

http://www.picoauto.com/tutorials/knock-sensor.html

http://garage.grumpysperformance.co...-octane-for-compression-ratio.2718/#post-7057

as octane levels drop AND/OR when air temperature increase the chance of detonation (KNOCK) INCREASE

http://tpiparts.net/85_89_maf_sensors/
http://www.blowerworks.net/

one major restriction to and TPI system running a stock MAF sensor is they are rather airflow restricted
due too both design and internal size, http://www.blowerworks.net/ sells custom 3" 3.5" and even 4" custom built MAF sensor designs,
obviously youll need a set of 30lb-50 lb injectors to keep up with the potential increased air flow and the controller that will also work with the custom parts

85-89 MAF TPI Systems

Below is a list of all the needed sensors to install a MAF TPI setup, and each of their functions.

Mass Air Flow (MAF) Sensor: This sensor is responsible for measuring air volume and density. It is located in the air duct, before the throttle body. All of the air that the engine consumes must first pass through the MAF sensor. At the center of the MAF, is a very thin wire whose resistance increases as it goes up in temperature. A constant voltage is applied to this wire. Air being drawn through the MAF has the effect of cooling this wire, which lowers its resistance, and increases current. As you might suspect, the more air is drawn through the MAF sensor, the greater the current flow. It is important to note that hot dry air is less dense and has less mass than cool moist air. As a result, hot dry air will cool the wire less than cool moist air.

A circuit mounted on the MAF sensor serves to convert the current flow into a variable frequency square wave on 1985 models, which is sent to the ecm. MAF units from 86-89 models output a simple analog signal instead of using frequency modulation like the 1985 units. The ecm will calculate the amount of fuel needed depending on the signal from the MAF sensor. It is very important that there are no air leaks (from a ripped air duct for example) between the MAF and the throttle body.

Oxygen Sensor: Responsible for determining the amount of oxygen in the exhaust manifold. Depending on how much oxygen is in the exhaust, the ecm can determine whether or not the air/fuel mixture is rich or lean. The signal sent to the ecm by the ecm varies between 0.0 and 1.0 volts. An ideal mixture (also known as a Stoichiometric mixture) of 14.7:1 is represented by .450 volts. If the oxygen sensor voltage is below .450, then the air/fuel mixture is lean. Anything over .450 means the mixture is rich. Since the sensor is essentially just a switching device, it will be fluctuating alot between lean and rich. This is normal, and an indication that the sensor is in working properly.
Keep in mind however that oxygen sensors (except wideband oxygen sensors), are not very accurate below or above .450 volts. Exhaust gas temperature will affect the oxygen sensor reading as well. The sensor will not read properly until exhaust gas temperature reaches approximately 600 degrees Farenheit. If you have headers installed, it is a good idea to use a heated oxygen sensor (3 wire) instead of the usual single wire sensor. Headers usually place the oxygen sensor further down the exhaust stream, where exhaust temperatures are cooler. A heated oxygen sensor will heat itself, allowing a more reliable sensor reading than a single wire sensor. If you have factory exhaust manifolds, then the single wire sensor is adequate.

Oxygen sensors are a regular maintenance item, and should be replaced every 30,000 miles. When an oxygen sensor goes bad, it tends to read lean, and will not fluctuate very much. The ecm will attempt to correct this false lean condition by richening the mixture. This will cause poor driveability, and high gas consumption.

Knock Sensor: Also known as detonation sensor, it is responsible for sensing spark knock. Basically, thats when the fuel mixture ignites before the spark plug fires. The piston is moving upwards as this premature combustion takes place. Since fuel is used to cool down the combustion chamber, a lean condition causes the temperature to rise, and ignites the fuel mixture prematurely. This is very abusive on the engine internals, and reduces the life of any engine. The more powerful the engine, the greater the potential for damage. Detonation can be cause by a variety of things. One of the more common causes on TPI retrofits where prom changes have been made to the fuel or spark tables is a lean condition. It isn't always loud enough to be heard, so just because you don't hear any pinging, doesn't mean its not happening.
Detonation will cause a vibration to travel through the engine block. The sensor listens for this vibration at a certain frequency, and sends a signal to the ecm when the frequency is heard. This frequency is different depending on engine size. To prevent possible engine damage, the spark timing needs to be retarded when detonation is present. The sensor itself does not pull the timing back however. The ecm is in charge of retarding the timing, and will do so according to a series of settings inside the prom. The knock sensor is located on the passenger side of the engine block on factory applications. It can however be relocated to the driver side of the block if needed (header clearance for example). They are different depending not only on the size of the engine, but also the ecm being used. It is important that the correct sensor is used to avoid problems. Although it is possible to run the car without one, I strongly suggest against this. I have had customers come to me looking for a $45 knock sensor after spending several hundred dollars and an extra month of work rebuilding a blown engine due to detonation.

Throttle Position Sensor (TPS): Responsible for reporting to the ecm the position of the throttle blades. The ecm will receive a signal which can vary from 0.0 to 5.0 volts. At idle, the TPS should be read .54 volts (factory specification) unless it has been set to a different value inside the prom. If it does not read .54 volts and the idle TPS voltage setting has not been modified in the prom, then it should be adjusted. Under full throttle, it should output close to 5.0 volts. Throughout its range of motion, the voltage should climb steadily, without any jumps or falls. If it is not steady or has some fluctuations as it is moved through its range of motion, it should be replaced. This sensor is located on the passenger side of the throttle body.
Coolant Temperature Sensor (CTS): This is basically a thermistor (means that it changes resistance with temperature) that supplies the ecm with the temperature of the engine coolant. This temperature reading is used for several important functions. The most notable is that the ecm adds extra fuel to an engine when its cold, and as the engine warms up, the extra fuel is reduced. This sensor mounts at the front of the intake manifold. The chart below shows the approximate resistance for this sensor in relation to temperature.

Intake Air Temperature Sensor (IAT): This sensor is also a thermistor (means that it changes resistance with temperature) that supplies the ecm with a temperature reading of the air being drawn into the engine. It is the same as the coolant temperature sensor on 86-92 models. The 1985 intake air temperature sensor used a different connector and cannot be used as a coolant temperature sensor because it had an exposed bulb. This sensor mounts underneath the plenum. The chart above shows the approximate resistance for this sensor in relation to temperature.
Idle Air Control (IAC) Valve: Although this is technically not a sensor at all, people often treat it as one. It is responsible for regulating the amount of airflow being admitted into the engine to adjust engine speed, particularly at idle and deceleration. The ecm controls the IAC at its discretion. The IAC works by moving a cone shaped pintle, which can extend and retract as needed to admit or block off incoming air. The valve moves the pintle in "steps". These steps are numbered and range from 0 to 160. A properly adjust throttle body should be idling when warm between 15-25 steps.

The IAC is used under a variety of conditions, not only at idle speed. The valve mounts on the bottom coolant plate of the throttle body.

Vehicle Speed Sensor (VSS): This is responsible for providing the ECM with the vehicle speed. It can be located either at the tailshaft of the transmission, or behind the speedometer on cars with a cable driven speedometer. It sends a 2k ppm (pulse per mile) square wave signal, and is needed for a variety of functions. It is absolutely critical for the ecm's learn mode, timing retard, emissions, torque converter lockup (automatic lockup transmissions only), idle speed control, and to avoid stalling on deceleration. It is possible to run without one. However, your car will NOT be street legal if you are required to retain emissions equipment, the ecm will not control the torque converter lockup, the ecm will not retard timing if you run into detonation, and it is possible to run into stalling /idle speed issues. In addition, the ecm will not adjust the fuel table properly as you drive (known as its "learning ability"). If the ecm does not know the vehicle speed it is assumed to be 0 mph.

If you still insist on not running a vss, I very highly suggest that the minimum vehicle speed for timing retard be brought down to 0 mph in the prom. The factory setting is 2 or 3 mph. If you don't bring this value down, and you do not run a vss, the ecm will NOT retard your timing under detonation.

http://tpiparts.net/90_92_speed_density_sensors/

90-92 Speed Density TPI Systems

Below is a list of all the needed sensors to install a speed density TPI setup, and each of their functions.

Manifold Absolute Pressure (MAP) Sensor: This sensor is responsible for measuring manifold air pressure. In simple terms, it measures engine vacuum inside the intake manifold. The lower the vacuum reading, the greater the load on the engine (i.e. heavy acceleration). The higher the vacuum reading, the lower the load on the engine (i.e. cruising or light throttle). The ecm needs this information to calculate how much fuel the engine needs. An engine under heavy load will require more fuel than an engine under light load. The MAP sensor is usually located on a bracket on the passenger side of the plenum. It may however be mounted on the firewall, or somewhere close by.

The ecm will see a signal from the MAP sensor which will vary from 0.0 to 5.0 volts. Under full throttle (0" of vacuum), it should read close to 5.0 volts. The voltage should drop depending on engine vacuum as described by the chart below:

Oxygen Sensor: Responsible for determining the amount of oxygen in the exhaust manifold. Depending on how much oxygen is in the exhaust, the ecm can determine whether or not the air/fuel mixture is rich or lean. The signal sent to the ecm by the ecm varies between 0.0 and 1.0 volts. An ideal mixture (also known as a Stoichiometric mixture) of 14.7:1 is represented by .450 volts. If the oxygen sensor voltage is below .450, then the air/fuel mixture is lean. Anything over .450 means the mixture is rich. Since the sensor is essentially just a switching device, it will be fluctuating alot between lean and rich. This is normal, and an indication that the sensor is in working properly.

Keep in mind however that oxygen sensors (except wideband oxygen sensors), are not very accurate below or above .450 volts. Exhaust gas temperature will affect the oxygen sensor reading as well. The sensor will not read properly until exhaust gas temperature reaches approximately 600 degrees Farenheit. If you have headers installed, it is a good idea to use a heated oxygen sensor (3 wire) instead of the usual single wire sensor. Headers usually place the oxygen sensor further down the exhaust stream, where exhaust temperatures are cooler. A heated oxygen sensor will heat itself, allowing a more reliable sensor reading than a single wire sensor. If you have factory exhaust manifolds, then the single wire sensor is adequate.

Oxygen sensors are a regular maintenance item, and should be replaced every 30,000 miles. When an oxygen sensor goes bad, it tends to read lean, and will not fluctuate very much. The ecm will attempt to correct this false lean condition by richening the mixture. This will cause poor driveability, and high gas consumption.

Knock Sensor: Also known as detonation sensor, it is responsible for sensing spark knock. Basically, thats when the fuel mixture ignites before the spark plug fires. The piston is moving upwards as this premature combustion takes place. Since fuel is used to cool down the combustion chamber, a lean condition causes the temperature to rise, and ignites the fuel mixture prematurely. This is very abusive on the engine internals, and reduces the life of any engine. The more powerful the engine, the greater the potential for damage. Detonation can be cause by a variety of things. One of the more common causes on TPI retrofits where prom changes have been made to the fuel or spark tables is a lean condition. It isn't always loud enough to be heard, so just because you don't hear any pinging, doesn't mean its not happening.

Detonation will cause a vibration to travel through the engine block. The sensor listens for this vibration at a certain frequency, and sends a signal to the ecm when the frequency is heard. This frequency is different depending on engine size. To prevent possible engine damage, the spark timing needs to be retarded when detonation is present. The sensor itself does not pull the timing back however. The ecm is in charge of retarding the timing, and will do so according to a series of settings inside the prom. The knock sensor is located on the passenger side of the engine block on factory applications. It can however be relocated to the driver side of the block if needed (header clearance for example). They are different depending not only on the size of the engine, but also the ecm being used. It is important that the correct sensor is used to avoid problems. Although it is possible to run the car without one, I strongly suggest against this. I have had customers come to me looking for a $45 knock sensor after spending several hundred dollars and an extra month of work rebuilding a blown engine due to detonation.

Throttle Position Sensor (TPS): Responsible for reporting to the ecm the position of the throttle blades. The ecm will receive a signal which can vary from 0.0 to 5.0 volts. At idle, the TPS should be read .54 volts (factory specification) unless it has been set to a different value inside the prom. If it does not read .54 volts and the idle TPS voltage setting has not been modified in the prom, then it should be adjusted. Under full throttle, it should output close to 5.0 volts. Throughout its range of motion, the voltage should climb steadily, without any jumps or falls. If it is not steady or has some fluctuations as it is moved through its range of motion, it should be replaced. This sensor is located on the passenger side of the throttle body.
Coolant Temperature Sensor (CTS): This is basically a thermistor (means that it changes resistance with temperature) that supplies the ecm with the temperature of the engine coolant. This temperature reading is used for several important functions. The most notable is that the ecm adds extra fuel to an engine when its cold, and as the engine warms up, the extra fuel is reduced. This sensor mounts at the front of the intake manifold. The chart below shows the approximate resistance for this sensor in relation to temperature.

Intake Air Temperature Sensor (IAT): This sensor is also a thermistor (means that it changes resistance with temperature) that supplies the ecm with a temperature reading of the air being drawn into the engine. It is the same as the coolant temperature sensor on 86-92 models. The 1985 intake air temperature sensor used a different connector and cannot be used as a coolant temperature sensor because it had an exposed bulb. This sensor mounts underneath the plenum. The chart above shows the approximate resistance for this sensor in relation to temperature.

Idle Air Control (IAC) Valve: Although this is technically not a sensor at all, people often treat it as one. It is responsible for regulating the amount of airflow being admitted into the engine to adjust engine speed, particularly at idle and deceleration. The ecm controls the IAC at its discretion. The IAC works by moving a cone shaped pintle, which can extend and retract as needed to admit or block off incoming air. The valve moves the pintle in "steps". These steps are numbered and range from 0 to 160. A properly adjust throttle body should be idling when warm between 15-25 steps.

The IAC is used under a variety of conditions, not only at idle speed. The valve mounts on the bottom coolant plate of the throttle body.

Vehicle Speed Sensor (VSS): This is a magnetic speed sensor mounted on the transmission that sends a 4k ppm (pulse per mile) sine wave signal to the ecm. It is responsible for suppling the vehicle speed to the ecm. This is needed for a variety of functions. It is absolutely critical for the ecm's learn mode, timing retard, emissions, torque converter lockup (automatic lockup transmissions only), idle speed control, and to avoid stalling on deceleration. It is possible to run without one. However, your car will NOT be street legal if you are required to retain emissions equipment, the ecm will not control the torque converter lockup, the ecm will not retard timing if you run into detonation, and it is possible to run into stalling /idle speed issues. In addition, the ecm will not adjust the fuel table properly as you drive (known as its "learning ability"). If the ecm does not know the vehicle speed it is assumed to be 0 mph.

If you still insist on not running a vss, I very highly suggest that the minimum vehicle speed for timing retard be brought down to 0 mph in the prom. The factory setting is 2 or 3 mph. If you don't bring this value down, and you do not run a vss, the ecm will NOT retard your timing under detonation.

TPI Torque Specifications

Below are the torque specifications as designated by GM for Tuned Port Injection intakes. Please note that some specifications are in lb. ft., and some are in lb. in.

Manifold to Runner Bolts 25 lb. ft. Runner to Manifold Bolts 25 lb. ft.
Fuel Rail Attaching Bolts 15 lb. ft.
Throttle Body Attaching Bolts 18 lb. ft.
Throttle Position Sensor 18 lb. in.
Idle Air Control Valve 13 lb. ft.
Throttle Body Coolant Plate 27 lb. in.
Throttle Body Cover Plate 30 lb. in.
Power Brake Vacuum Fitting 108 lb. in.
Fuel Line Nuts 20 lb. ft.
Fuel Tube Bracket Bolt 25 lb. ft.
Fuel Pressure Connection 115 lb. in.
Pressure Regulator Base to Rail 44 lb. in.
Pressure Regulator Bracket 44 lb. in.
Outlet Tube to R/H Rail Retainer 44 lb. in.

Grumpy · Oct 28, 2017

yeah! I've seen way too many automotive components that were purposely designed to be absolutely non-repairable, once they failed.
especially stupid things like sensors that were purposely designed with a resistor or transistor or therm-mister , thats amp or voltage rated to just barely have the required capacity to function, that were manufactured with a component or two, that probably costs under 30 cents , that get poured solid with something like epoxy resin.
this obviously makes the access to the defective and normally easily replaced component that failed , almost impossible to test and if required replace, just so they can charge you several hundred times the cost of the failed sub-component you could normally test, diagnose and replace for under 30 cents , forcing you to purchase a complete new component.
it generally helps if you look up both the cost of the new replacement component and the electrical schematic and look up any testing info
https://www.summitracing.com/parts/anm-cp7838

and rev the engine a few times and watch the fuel pressure it should in theory remain in the 38 psi-42 psi range for most TPI and TUNED PORT efi

having a few basic meters,gauges etc. helps

http://garage.grumpysperformance.com/index.php?threads/my-tool-list.228/#post-267

MULTI METER

INFRARED TEMP GUN

TIMING LIGHT

COMPRESSION GAUGE

PRESSURE/VACUUM GAUGE

this looks interesting with a discount coupon its discounted to about $169.99 until 4/30/18 plus $49.99 for a two year 100% warranty

http://garage.grumpysperformance.co...pro-scanner-harbor-freight-zurich-zr13.14833/

if you purchase a ZR13 auto code scanner, from HF,
you need this info
DOWN-LOAD AND PRINT IT OUT!

https://manuals.harborfreight.com/manuals/63000-63999/Q63806.pdf

https://manuals.harborfreight.com/manuals/63000-63999/63806.pdf

https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore,f,EAFeatured+Weight,f,Sale+Rank,f&q=zr13

Last edited: Oct 14, 2018

https://www.zip-corvette.com/85-89-high-performance-adjustable-maf-sensor.html
85-89 High Performance Adjustable MAF Sensor

Item Number: EH-521
http://www.chevythunder.com/fuel injection elect. pg B.htm

http://www.chevythunder.com/fuel injection elect. pg B.htm

heres a rather useful addition to the older c4 corvette tuning world, its a new (yes expensive)
but adjustable and thus some what tune-able MASS AIR FLOW SENSOR for the TPI corvettes

Sensor
EMISSION COMPONENT LOCATIONS

Sensor

Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor

Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.

Grumpy · Jul 17, 2019

info that might help (before you ask, yeah the LT1 is very similar)

L-98 Engine Start Sequence

knowing whats going on and WHY can help

http://members.shaw.ca/corvette86/Co...0View%2086.pdf

http://garage.grumpysperformance.com...t1-vette.1401/

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.

Engine "Catches":

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.

Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

http://www.harborfreight.com/cpi/cta...emnumber=46030

Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

Theory of Operation

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

MAF Operating Conditions

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

MAF Problems

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

this flow chart might help

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

MAF Mods

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.
Welcome to C4 vette codes it is very ....repeat very
important that if you are not savvy of working on your
vette ...you would be better off - taking your car to a
dealership for repairs on your trouble codes.
However if you feel that you want to dive right in ..than you
have come to the right place.First locate your car's alcl
this component is located just below the instrument panel and
to the left of the center console. Remove the plastic cover
the first two slots to your right are the A & B slots for a drawing of
the alcl module's picture is added below.
The A slot is the diagnostic slot and the B slot is the ground
slot. insert the computer key into these slots (with the engine
off) this is very important...now only put the ignition key
to on ( not start !!!) the check engine light will display a
code 12 which is one flash followed by two flashes.
this code will be flashed three times ..followed by the
trouble code stored in your car's computer.
what ever the code is it will be flashed three times.
have a paper and pencil ready and write down the
code .

code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
please remember that if you have the computer key installed
in the alcl and you start the engine ( you will ruin the engine's computer
)
only put the ignition to on (not to start)
If you should get a check engine soon display.. you can use
the above procedure and codes to buy the right part
or at the very least to keep from getting taken for a ride
and be made to pay hight prices for some inexpensive
module that you could have installed yourself.
You never ask a barber if you need a haircut ..
so you have to be on guard they will see you comming
a mile away.
If your engine displays a trouble code ... your engine will
go into limp mode ..it will still run but very poorly.
you might be able to reset the computer if it will not start
( just to get home ) by disconnecting both battery cables
and re-installing them ...this is not recommended ..but if
you are stranded it might help unitl you get your car home
or to a repair shop..good luck

1985 TO 1991:

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.

ECM CODES 1992 TO 1993:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.

CODES 1994 TO 1996:

DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.
_________________you really can,t be effectively at playing mr-fix-it with out the correct tools

especially on the more modern cars that are computer controlled, the days of effectively tuning by ear and vacuum gauge and engine sound went out with carbs
you need a few basic tools, now the list will vary, but you can,t get by by guessing, you neet to know and test now that sensors and CPUs control engine function
heres some basic tools

be sure to get the specific manuals your car and EFI system and ignition system,require FIRST

https://www.etoolcart.com/index.asp?...OD&ProdID=4047

while it appears to be expensive, it saves you a good deal of money in the long run compared to dealing with the local chevy dealers mechanics, and makes diagnostics far faster, I bought this for the shop and it seems to be a good investment, since between a dealers diagnostics and swapping parts that don,t need changing you could easily spend close to that on just a few problems getting sorted out
youll also want a few basic diagnostic tools

https://www.etoolcart.com/index.asp?...OD&ProdID=4417

https://www.etoolcart.com/index.asp?...OD&ProdID=6688

https://www.etoolcart.com/index.asp?...OD&ProdID=2597

https://www.etoolcart.com/index.asp?...OD&ProdID=8108

and a book or two

http://www.amazon.com/gp/product/0837608...ce&n=283155

http://www.amazon.com/gp/product/0879387...ce&n=283155

http://www.amazon.com/gp/product/0760304...ce&n=283155

in no time youll be the area wizz kid on chevy injection diagnostics

This is from http://shbox.com/

A fuel pressure test gauge can be bought at your local auto supply for ~$35. Attach it to the schrader valve that is on the fuel rail. Schrader valve location on 1994-1997

Normal pressure when the engine is not running and lines have been pressurized is 41-47 psi. This same pressure should be observed at wide open throttle (WOT). WOT can be simulated by removing the vacuum hose to the regulator at idle. At idle (because of the effect of the vacuum to the regulator) pressure will be less than what you observe with the vacuum line off. There may be anything from a 3 to 10 psi difference. NOTE: any indication of fuel in the vacuum line to the regulator, means the regulator is leaking and should be replaced. Check the line for fuel or the smell of fuel.
To fully determine that you don't have a pressure drop off during actual WOT situations, you should tape the gauge to your windshield and take it for a test run. This will tell you if the pump can meet actual fuel flow demands at pressure and not just at a simulated WOT condition (as when removing the vacuum to the regulator).
When you have a gauge connected and the pressure looks initially good and then bleeds off quickly when you shut the engine off, you can do a couple of tests to help you figure out where the pressure loss is.
What the factory manual says to temporarily install, is a set of "fuel line shut off adapters" (probably something the normal guy is not going to have available). You remove the fuel lines from the rail and connect these valves in between. This lets you shut off either side of the lines for testing.
You can do the same thing by pinching the flexible lines to shut them off, but risk breaking them. You might be able to do it (your risk) by using a needle nose vise grips and putting some scrap hose as cushions on the jaws. Then use that to clamp off the line just enough to seal it. Obviously, this is not the best way to shut off the lines and could result in breakage. Heat and age can make the hoses brittle. If you don't want to risk it, don't. It's just a suggestion.
You can use the fuel pump prime connector for pressurizing the system (jumper 12v to it to run the pump).
Watch your gauge as you jumper the prime connector. When you have good pressure remove the jumper and clamp off (or use shut off valve) the fuel supply line (3/8 pipe). If pressure holds, you have a leak on the feed line somewhere before it gets to the clamp (or shut off valve) or at the check ball in the pump. If it still goes down, release your clamp (or open shut off valve). Pressurize the system again, then remove the jumper and this time clamp (or shut off) the return line (5/16 line). If pressure holds, then the regulator is faulty. If pressure does not hold, you need to locate leaky injector(s). If you can't tell a leaky injector from reading the plugs, you can look and see if injectors are leaking by removing the fuel rail screws and pull the rail and all the injectors up, so you can see under them. Leave them over the injector ports. Pressurized the system and look under the injectors to see if any are dripping.

Grumpy · Jul 17, 2019

not mine but thought I would share, not bad tips...

Here are some of the more common things I've seen with the 1984 CrossFire system.

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

http://www.chevythunder.com/fuel injection elect. pg B.htm

* Coolant Sensor is faulty - the gauge gives a false sense that it's doing okay, but the sensor that the ECM reads is totally separate from the one the gauge reads! Pinging on acceleration during warmer runs are noticed. If in doubt, just replace the thing. The one the ECM reads is in the FRONT of the manifold - has two wires (black and yellow) going to it.
* Throttle Position Sensor is faulty; can give strange results. Bad idle, great high-RPM power. Always good idea to check this thing out. Uses a +5v reference to send voltage to the ECM. Neat trick: setup the output (center wire) to where it switches to full +5v with the flip of a switch. Makes the ECM think you're at full-throttle when you're not. (Good for acceleration with an automatic tranny, which is all the crossfires ever came with that I know of.)
* MAP sensor - this thing reads in the amount of manifold vacuum and sends out a voltage to the ECM. If it's not getting the correct voltage, you can get pinging real bad on acceleration at any temperature. Pull the wires off. If the idle improves, you have a faulty one. Replace it.
* Bad O-rings or filters on injectors. Turn the key, but don't start the motor. Have the aircleaner assembly off and observe the injectors. If they leak, replace the o-rings and injector filters. If they still leak, replace the injectors!
* Bad O2 sensor. Runs rich sometimes. Won't pass emissions for sure! Is suggested to replace every 30k miles or so. They cost around $25 and are a snap to replace. Not a bad idea to replace if you're going to get under the car in the first place. You can run a wire inside your car and read the voltage with a DMM to see what your air/fuel ratio is.
* Spark Plugs fouling.. often this is due to bad valve seals. One of my tricks is to uncover the plug electrode by "side gapping" the plugs.
* Knock Sensor.. I think this is my problem right now. The "Computer Codes" book said it causes light pinging during acceleration on light loads.

while I very briefly worked at a chevy dealership as a mechanic
(I was 18 at the time)
I learned the most simply by owning several corvettes for decades
(always have owned one or more,since the 1968)
(currently own a 1985 and 1996)
and having built well in excess of 140 plus engines you eventually are forced to learn a few things along the way
,and while that may sound like a lot of engines,
its only 3-5 engines a year over the last 48 years ,
and at one point I was doing it as a side business, knocking out 1 or more carefully assembled engines a month.

Grumpy · Jul 17, 2019

http://www.rowand.net/Shop/Tech/GMTPISwap.htm

GM TPI Swap
This page is for information about GM Tuned Port Injection EFI swaps. TPI is a fuel injection system that uses individual injectors for each cylinder that are mounted in the intake manifold and usually ends up looking much different than a traditional carbureted setup.

For general-purpose EFI information, please refer to my EFI Basics page. For GM TBI systems, please refer to my GM TBI Swap page. For Ford systems, please refer to my Ford EFI Swap page.

Goals for this Project and Web Page
This page is where I'm gathering information and details about the GM TPI swap I'm working on for one of my 1973 Buick Electra. If it goes well on the first one, I'll likely try to replicate the swap onto my 1970 Buick Electra and possibly even my 1958 Buick Special.

My main goal here is a "DIY" style EFI swap using as many low-cost pieces as possible. If you know something about wiring and basic EFI bits (or can read up and learn), then this is something any person could replicate. Basically, I am trading my time to think about things and learn how stuff works for the money I could pay someone else to do that work for me. I like to learn about stuff, and I'm always short on cash, so this is a good set of trade-offs for me. If you have more money than common sense, the thought of building your own wiring harness scares the hell out of you, or you don't want to invest the time or energy into thinking about this too much, then go pay someone else for the right parts.

A secondary goal is to avoid cutting and hacking at the vehicle to actually do the swap - particularly in the case of my 1970 Buick Electra, where being able to return the vehicle to "factory stock" for a later restoration help retain the car's value. This means no cutting or changing of the gas tank or the firewall. This pretty much dictates a weatherproof computer that can be mounted in the engine compartment.

As part of an aggressive focus on low-cost, I am attempting to build my own harness out of factory bits. If you do not want to go that route, various sources for custom "EFI swap" harnesses are available, go Google for them. I prefer to wire things myself and want to be able to take a pile of wire stubs and connectors and turn them into a wiring harness for just the cost of the wire and some new terminals to go into the connectors.

This page is focused on the "hardware" for this swap - the computer, sensors, actuators, solenoids, pumps, relays, and the wiring harness to tie it all together. It is not meant to address how to tune the resulting TPI system after you create it. That topic already fills many books and many websites, and is far too much to cover here.

Basic Choices
First up, many people will be asking "Why TPI instead of TBI?", and it's a valid question. It's true that TPI (Tuned Port Injection) is a bit harder to swap on than TBI (Throttle Body Injection) because it requires an intake manifold capable of holding the individual fuel injectors for each cylinder. TBI mounts much like a carburetor, and can be added using an adaptor plate, so it's simpler to mount. They both use the same basic sensors, though the computer used to drive each one is a bit different. TPI also requires more fuel pressure, so it needs a different fuel pump, but the fuel system requirements/designs are pretty similar. TPI does allow for finer fuel control in more advanced systems, though TBI does a pretty darned good job on a stock or reasonably-close-to-stock engine. I prefer TPI for the potential added control, though I fully admit than in my circumstances that may be more of a "looks cooler to me" type of decision and your thoughts may vary. But, since this is my page and my cars, my opinion counts for a lot no matter how biased it may be.

In my case, I have chosen a TPI system that uses a computer that is weatherproof and is placed in the engine compartment - see the next section for more details on that. That means the huge bundle of wires that usually has to go through the firewall is not needed - you just need a few key wires to go into the passenger compartment, mainly the park/neutral sensor, SES (Service Engine Soon) light, and the ALDL (Assembly Line Diagnostic Link) connector. On an older vehicle where you want to avoid cutting holes in the firewall, this is a very big deal, and to me, this helps make it worth it for the added hassle that TPI brings.

Also, mounting a TPI system onto an engine that was never offered with TPI means you have to make up some custom hardware to get it to work. Getting the fuel rails fabricated, the intake manifold modified to accept the fuel rails, and getting a throttle body mounted to the intake manifold are all difficult tasks. I say "difficult" not because these are insurmountable goals, rather that they are hard for the average DIY-er to do in their garage. That translates into having to spent money to pay someone else to do the work for you, which is at odds with the need to make this as DIY and low-cost as possible. Welcome to the world of tradeoffs. The good news is that once you get the basic hardware in place, upgrades to larger injectors, sequential injection and other higher-end goodies are as "simple" as swapping out the wiring harness and computer. And yes, I do realize that using the term "simple" for that will strike many folks as very odd. Remember, wiring doesn't scare me and is something I can do easily. Machining parts is something I find a lot harder to do.

Computer
The computer I chose is computer part #1227727. This computer is electrically identical to one of the most popular GM TPI computers - computer part #1227730- except that this one is in a weather-proof housing that can be mounted under-hood. The #1227727 computer was used in both V6 and V8 models - most notably in the Corvette for 1990 and 1991. The V6 applications are various W-body vehicles from 1988 through 1993 on either the 2.8L (1988-1989) or 3.1L (1989-1993) engine. Sometimes the computer carries #16197128 or #16198260, but they should all be functionally interchangeable for the purposes of this swap. Other I4 and V6 engines with different computers were available in the W-bodies during this time, so double check the engine and computer info before you grab any parts. More information can be found via Googling for the computer number. The W-bodies in that era include the Buick Regal, Chevy Lumina, Oldsmobile Cutlass, and Pontiac Grand Prix.

My research indicates that the V6 and V8 units on this computer are identical except for the MEMCAL (Memory Calibration Unit) and specific programming burned onto the main "chip" that is on the MEMCAL. The MEMCAL itself is available from the dealer for a reasonable cost, as well as being around used. The chips are readily available from various sources, and I'll need one of those no matter what. That means the biggest issue here with using a V6 computer is tracking down a V8 MEMCAL - I'll be burning a new chip for it with my custom program no matter what. Given the cost difference between a "common V6 computer" and a "rare V8 Corvette-only" computer, starting with the V6 computer should be a much better deal. At the very least I got an actual #1227727 computer to do my mock-up work with for only $40.

For those out there asking "What the heck is a MEMCAL?", the MEMCAL contains the ESC (Electronic Spark Control) and "limp home" circuitry. The main "chip" (EPROM) plugs into the MEMCAL which in turn plugs into the computer. See the pictures below for more details on what they look like and how to remove/install them.

All of the sensors and injectors are pretty much standard fare for the V6 and V8 units, so if you find one of these cars, I'd say you should just grab as much as you can including the entire wiring harness and every sensor you can find/reach/remove. One thing to note is that the lb/hr rating on the injectors might not be appropriate for your needs, but they're fine for mock-up and maybe even initial testing of the system. If the injectors are too small, they will not be able to "keep up" at higher RPM and/or engine loads and the engine can go very lean causing costly engine damage. Basically, be sure you get an appropriately sized set on injectors for your engine.

I eventually found a running 1992 Chevy Lumina for sale locally for $100 and bought that to use as a source for the various parts for this swap.

Below is a "crib sheet" you can print out for use in any junkyard hunting for the computer and associated EFI parts. Millions of these cars were built, so finding one to grab parts from shouldn't be too hard. On the other hand, if you happen to come across a 1990 or 1991 Corvette you can pirate for these parts and the stuff is actually reasonably priced, then by all means, grab what you need along with the rest of the Unobtanium you find at the same time. The rest of us will stick to something we might actually find for a decent price - and we'll also continue to hate those of you who somehow manage to find a great deal on real Corvette parts.

the "PROBLEM" is most people won't take the time or effort to diagnose a problem by logically isolating and testing each component before the parts are replaced,
and yeah its basically a two step problem, that having a SHOP MANUAL, for your particular year corvette ,
and a few basic tools like a FUEL PRESSURE GAUGE,MULTI METER, AND TIMING LIGHT, COMPRESSION TESTER,
and a CODE READER MAKE FAR EASIER, ISOLATE AND TEST ARE THE BASICS OF ANY REPAIR PROCESS>
you first have to understand how each component functions and how to test its functioning correctly.
it helps a great deal if you know the basics and have access to the tools required to test.
it helps a great deal if you understand how the various sub systems like ignition,
timing and terms like AMPS. VOLTS,RESISTANCE, and fuel delivery work, terms LIKE PRESSURE, VOLUME, and the basic 4 cycle engines design parameters.
theres not a single problem on a C4 CORVETTE, that can't be diagnosed with a shop manual, fuel pressure gauge, multi meter, exhaust back pressure gauge/vacuum gauge and an accurate infrared temp gun, timing light, compression/leak down tester, basic mechanics tools, a set of jack stands and a floor jack.
and a logical isolate and test mentality, if you have access to the internet to ask questions about related tests, PROVIDED you ask the correct questions and test to find the related answers,
yeah, having experience helps and tools like code scanners, degree wheels, dial indicators , a dial caliper, feeler gauges certainly help,
but you can solve problems by simply understanding how components are supposed to work, and how they can be tested to verify they are defective or not!

related info
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-88488

http://garage.grumpysperformance.com/index.php?threads/bare-minimum-tools.11026/#post-48779

http://garage.grumpysperformance.co...too-common-questions-can-be-found-here.12892/

http://garage.grumpysperformance.com/index.php?threads/leakdown-compression-test.881/#post-56489

http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.com/index.php?threads/c4-and-camaro-sensor-and-relay-switch-locations-and-info.728/#post-93194

http://garage.grumpysperformance.com/index.php?threads/optispark-ignition-info.628/#post-75647

http://garage.grumpysperformance.com/index.php?threads/under-car-safety.26/

https://www.testequipmentdepot.com/extech/thermometers-and-humidity-meters/infrared-thermometers/high-temperature-infrared-thermometer-58to1832f-50to1-laser-pointer-42545.htm?utm_source=bing&utm_medium=cpc&utm_campaign=NEXT%20-%20Bing%20Shopping%20-%20Extech&utm_term=1100200223789&utm_content=All%20Extech%20Products

C4 and camaro sensor and relay/switch locations and info

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The Grumpy Grease Monkey mechanical engineer.

The Grumpy Grease Monkey mechanical engineer.

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The Grumpy Grease Monkey mechanical engineer.

The Grumpy Grease Monkey mechanical engineer.

The Grumpy Grease Monkey mechanical engineer.