the answers too those all too common questions can be found here!

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
about once or twice a month I get a question that,s basically asking some version, of
" WHY is my C4 corvette is running like crap, Failing too start or stalling"





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Ive often wondered ,how many of you gentlemen refer to these threads when , your faced with some problem or trouble code and your looking too isolate or clear that issue or problem?
IVE posted decades of related info, reference tables, test procedures and links that contain a wealth of related info, chances are excellent that if your willing to do the research the answer is here on most common issues, the only issue is that most people will refuse to take the time and effort to do the research and read far enough to locate the info they need.
most people are unwilling to learn how and why their cars systems work or how to test them correctly.want quick answers
the key to working on any corvette is to have access to a few diagnostic tools and a factory shop manual.
once you have the basic tools and the shop manual, you pull trouble codes, and think logically,a shop manual for your year car,a multi meter, a fuel pressure gauge, a vacuum gauge and pulling trouble codes and use of some logic rather than throwing up your hands and screaming goes a long way toward solving issues.
its simply a process of intelligently isolating and testing components, and adjusting or replacing those individual components, that fail testing procedures
obviously pictures and detailed instructions in the threads,help immensely
I know that I very regularly look at the threads and charts along with my factory shop manual for both ideas and procedures too follow when,
I start by pulling trouble codes and grabbing a multi meter in most cases.
I've had an issue, and its rare to not find either the answer or at least a few very helpful suggestions on what too test or where too test!
so how about you gentlemen?
I don,t care if its a brake upgrade or a dash indicator that's out,
the first step, in correcting the problem, is too look over the related reference material and related threads on the subject.

If theres one common concept that confronts almost all new corvette owners,
its a feeling that they are a bit overwhelmed,
theres no need to be, if you don,t let the seeming complexity of a the parts and how they work in a high performance car like a corvette,and a meriad of sub systems and sensors, get you confused or baffled,
when it comes to doing repair work, but if you take a few deep breaths and have a factory shop manual and a few basic testing tools handy, like a multi-meter and fuel pressure gauge youll find that intimidated feeling is un-waranted as most problems can be resolved with some research and careful testing!
ineviatably when I have someone bring over a C4 corvette , too the shop they seem overwhelmed by the complexity of finding the problems root cause, but once you explain how each individual sub-system and sensor operates, how each sensor effects the cars operation, and basics like checking sensors, fuses, and relays and electrical grounds, and how each can be checked to see if its functioning correctly, the testing process can rather quickly lead anyone with a shop manual and a few basic testing tools to an answer.
you might be amazed at how often a defective single blown fuse ,bad sensor, loose electrical ground, or locked up,relay can cause the car major problems!
knowing how you logically progress , too track down and issolate and test to find the source of the problem is the key here!

yes pulling trouble codes tends to help, but just using a bit of logic and the shop manual goes a long way here!
well the answers almost always the same in most respects, its going to take some time and effort to isolate and test to determine the problem, but its simply a mater , of running through the potential problem areas and testing , each, to prove or dis-prove the potential for that being the source of your particular issue.
If the engine spins and has good compression and oil pressure and your getting spark at the plugs , and the fuel rails and the fuels decent quality, it almost always comes down to the basics of compression, fuel delivery, ignition, ignition timing, spark for ignition, an electrical short, ground or defective sensor, there's also loose electrical connectors ,blown fuses,leaking vacuum hoses, etc. all of those issues are easy to isolate and test for! so don,t think of this is a complex issue its much more likely to be something your simply over looking!
yes it might be a defective part or somethinggs out of adjustment!
the way you fix it is the simple process of isolate and test! don,t guess, deal in facts! and don,t get frustrated, its really not that difficult if you think it through!

EMISSION COMPONENT LOCATIONS
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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
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http://www.professionalequipment.com/ex ... ermometer/
Wide temperature range from -58 to 1832°F (-50 to 1000°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.

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.

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you really need a scan tool of some sort to work on corvettes
THINK LOGICALLY< DON,T SKIP THE LINKS AND SUB LINKS
buy a CHEVY SHOP MANUAL FOR YOUR YEAR CORVETTE!
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 its a defective heat sensor or defective o2 sensor, 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
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http://www.harborfreight.com/5-in-1-dig ... 98674.html

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FLUKE is the brand of choice but they are expensive, shop around, Ive still got the original fluke multi meter I bought in HIGH SCHOOL and it STILL WORKS

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L98/ TPI Engine Start Sequence

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.

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.
youll find a hour or so reading thru the links and sub links, on this site in the threads, will provide a great wealth of related info and incite into related factors, or the function or testing of sensors, that you may not currently be thinking about, or things that you might not think that are related to your issue that PROBABLY ARE


without testing your simply guessing

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

http://garage.grumpysperformance.com/index.php?threads/drop-back-to-basics.12943/#post-67323

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772

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

http://garage.grumpysperformance.com/index.php?threads/no-start.16101/

http://garage.grumpysperformance.co...uble-shooting-flow-chart-info.11536/#post-783

http://garage.grumpysperformance.co...-test-seems-to-be-a-forgotten-art-form.11838/

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

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772
C4 Sensor Check Information
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

READ THRU THESE THREADS ALSO
viewtopic.php?f=80&t=728&p=9217&hilit=sensor+ohms#p9217

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

viewtopic.php?f=36&t=63&p=37970&hilit=multi+leads#p37970

http://garage.grumpysperformance.co...le-shooting-flow-chart-info.11536/#post-71845
BTW it generally helps if you post the city and state your in,
as theres at least some chance a local member,
may want to stop by and help you diagnose,
and maybe help rectify the issue if your LOCAL

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 a10 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 page so you can cross reference the code information with the sensor information.]

Sensor Location Measured Value
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohm @39 F.
Oil Pressure Sender/Switch. Top, left hand rear of engine. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 6PSI.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear. 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. Right side of engine, top right corner of radiator. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). Right side of throttle body at the front. .54 Volts Idle, ~ 5 Volts Full Throttle.
Assembly Line Communications Link (ALCL)
F E D C B A
G H J K L M
[The ALCL is located underneath the dashdoard, just below the instrument panel and left of center console.]
Top of page
Code Circuit or Sensor Possible Failures
13 Oxygen Sensor Circuit Check wiring and connectors. Bad Sensor
14 Coolant Sensor Circuit (High) Check wiring, connectors, thermostat. Monitor actual engine temperature. If within limits, and wiring and connector is OK, change thermostat and or sensor.
15 Coolant Sensor Circuit (Low) See above, particularly thermostat
16 Ignition Problems (Used only on 1992-1996 models) Direct Ignition (DI) Fault
21 Throttle Position Sensor (TPS) (High) Sticking or Misadjusted TPS. Also check wiring and connectors. Adjust or replace TPS.
22 Throttle Position Sensor (TPS) (Low) Sticking or Misadjusted TPS. Also check wiring and/ connectors. Adjust or Replace TPS.
23 Intake Air Temperature (Low) Measure sensor resistance with Digital Ohm meter. Must not be 0 ohms or infinite ohms. Replace if it shows one of these readings. Check wiring and/ connector of sensor. If OK, replace sensor.
24 Vehicle Speed Sensor (VSS) Only valid if vehicle moving. Check connections at ECM Check TPS setting. Possible ECM failure.
25 Intake Air Temperature (High) Measure sensor resistance with Digital Ohm meter. Must not be 0 ohms or infinite ohms. Replace if it shows one of these readings. Check wiring and connector of sensor OK.
26 Quad Driver Module Number 1 Check EGR, Canister Purge and AIR pump relays with a digital Ohm meter. A resistance of less than 18 ohms indicates a bad relay. If OK, potential ECM failure.
27 Quad Driver Module Number 2 Potential ECM or on a manual transmission car, potential upshift relay problem. Check relay, replace if less than 18 Ohms using a digital Ohm Meter.
28 Quad Driver Module Number 3 Air conditioning Clutch relay and/or cooling fan relays. Check with digital Ohm meter, replace if less than 18 Ohms. If relays OK, potential ECM failure.
32 Exhaust Gas Recirculation Circuit The most common cause of this code is a bad or intermittent EGR switch which is located on the EGR pipe between the exhaust manifold and the intake manifold. Replace this switch first when you get this code. Next, check electrical connections at EGR valve solenoid and then the ECM. Check all vacuum lines for leaks especially around the EGR valve. Possible ECM failure.
33 Mass Air Flow Sensor Circuit (1985-1990) Inspect intake system for leaks, Inspect for vacuum leaks, Check MAF connector and wiring, Check MAF for open using digital Ohm meter. Possible ECM failure.
33 Manifold Absolute Pressure High (1984) Check vacuum hoses. Check wiring to sensor. Change sensor. Check connections at ECM.
34 Mass Air Flow Circuit (1985-1990) Clean the throttle body. Check MAF connections. Replace MAF relay. Replace MAF Sensor. Possible ECM failure.
34 Manifold Absolute Pressure Low (1984) Check Vacuum hoses associated with MAP sensor. Check wiring and connections, particularly at ECM. Replace the sensor. Possible ECM failure.
35 Idle Air Control Circuit (IAC) Check fuel pressure, injectors, leaking throttle body. Change the IAC valve.
36 Mass Air Flow Burn Off Circuit Check connections at MAF, MAF relay and MAF Burn off relay. Check resistance of MAF relay and MAF burnoff relay with digital Ohm meter. replace if less than 18 Ohms. Possible ECM failure.
41 Cylinder Select Error Circuit (1985-1991) Check wiring at ECM. Possible PROM failure, or incorrectly seated PROM. Reseat PROM. Possible ECM failure.
42 Electronic Spark Timing Circuit (EST) Check wiring at ignition module. Replace ignition module. Possible ECM failure.
43 Knock Sensor Circuit Check ECM wiring. Replace knock sensor
44 Lean Exhaust Present Check wiring.connectors at Oxygen sensor. Check fuel pressure. Replace Oxygen sensor.
45 Rich Exhaust Present Check evaporation charcoal canister for smell of fuel (which normally comes from filling fuel tank to full). check fuel pressure regulator. Possible leaking fuel injector or sticking/bad EGR valve. Possible bad Oxygen sensor.
46 VATS Anti Theft Circuit Fault With negative battery lead disconnected and using high pressure, non residue contact spray cleaner, spray into area where ignition key inserts followed by inserting and removing key several times. Check for open/short on harness from steering column VATS ignition key to ECM. Possible defective anti-theft module.
51 PROM/EEPROM Error Faulty or incorrect PROM in the ECM. Change PROM with correct version for automobile.
52 Oil Temperature Circuit (Low Temperature) Check connections at the oil temperature switch. If OK, replace switch.
53 System Charging Voltage High or Low If voltage is more than 17.1 or less than 10 volts, this code will be set.Check battery leads, alternator drive belt for tightness and have electrical shop check alternator output. Voltage with engine off should be 12 volts. Voltage with engine running should be 14-15 volts. Use digital volt meter for checks and measure at the battery terminals.
54 Fuel Pump Circuit (Low Voltage) Using digital Ohm meter, check fuel pump circuits for shorts or opens.
55 Engine Running Lean This code is set when there is not enough fuel when accelerating. A possible fuel pump failure or insufficient fuel pressure due to a fuel line restriction is indicated.
62 Oil Temperature Circuit (High Temperature) Check wiring associated with Oil temperature switch. Replace switch.
63 Oxygen Sensor Circuit (Open) Check wiring and connections to Oxygen sensor.
64 Oxygen Sensor Circuit (Lean Exhaust) Check wiring and connections from Oxygen sensor to ECM. Check ECM ground terminal and battery ground. Check fuel pressure and fuel pump. Replace Oxygen sensor if all of above OK.
65 Oxygen Sensor Circuit (Rich Exhaust) Check evaporative charcoal canister for fuel fumes. Replace if contaminated. Check oil for presence of fuel. Check fuel pressure regulator, fuel pump, check for leaking injectors, Check for stuck/defective EGR valve, Replace Oxygen sensor if all above OK.
66 Air Conditioner Pressure Limit Exceeded Check the sensor electrical terminal connections and possible short to ground or open circuit in the pressure senor circuit senor wiring. Replace the Air Conditioning Refrigerant sensor.
67 Air Conditioner Pressure Limit Exceeded Check the pressure sensor or air conditioning clutch ciruit for possible short to ground or open circuit pressure sensor circuit in the sensor wiring.Replace the Air Conditioning Refrigerant sensor.
68 Air Conditioner Relay Fault Check the air conditioning relay circuit and the relay for possible short to ground or open circuit.
69 Air Conditioner Clutch Fault Check the air conditioning clutch circuit and the relay for possible short to ground or open circuit.
72 Gear Selector Switch Fault (Start Lockout) Check the connections at the TCC solenoid and Park Neutral switch. Replace the ECM or repair the transmission as needed.
[Info taking form 1984 thur 1996 Haynes Repair Manual]

having a few basic meters,gauges etc.
IT sure helps too have basic tools, when isolating issues
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MULTI METER
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INFRARED TEMP GUN
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TIMING LIGHT
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COMPRESSION GAUGE
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PRESSURE/VACUUM GAUGE
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THREADS WITH RELATED INFO AND LINKS
http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.co...-runs-rough-idles-and-sometimes-stalls.10688/

http://garage.grumpysperformance.com/index.php?threads/1986-vette-running-really-rich.9677/

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

http://garage.grumpysperformance.com/index.php?threads/cooling-off-that-c4-corvette.3954/

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

http://garage.grumpysperformance.co...-air-conditioner-on-cooling.12232/#post-59597

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.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-7017

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-54562

http://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-1

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

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

http://garage.grumpysperformance.com/index.php?threads/l98-corvette-wire-diagrams.11835/

http://garage.grumpysperformance.co...o-you-failed-emmision-testing.3522/#post-9307

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

http://garage.grumpysperformance.com/index.php?threads/spark-plug-info.202/

http://garage.grumpysperformance.co...-and-test-or-just-start-swapping-parts.15880/

http://garage.grumpysperformance.com/index.php?threads/timing-tabs-and-indicators.1015/

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

http://garage.grumpysperformance.co...ning-with-an-air-fuel-logger.6765/#post-25598

http://garage.grumpysperformance.com/index.php?threads/85-with-flicker-on-dash-and-radio.13593/

http://garage.grumpysperformance.com/index.php?threads/air-fuel-meters-and-tuning.268/#post-18435

http://garage.grumpysperformance.co...atio-or-infrared-thermometer.6174/#post-19287
 
Last edited:
youll find an extensive list of links in many threads,
while you may not be used to that format,
in this web site its very common
.
the links are there to provide a good deal or related info and help speed your research!
yes, youll typically find theres a good deal more info that you might have originally thought there might be,
and you run a minor risk of spending an hour our two learning in areas you never intended, too look into.
the result might be confusing at first,
you may find its an endless maze,
and ocasionally see duplicate posted info,
(keep in mind the object is to lead you to the related info,
no mater where you enter the web of threads related to your search.)
(and I fully admit the punctuation and spelling could be improved)
but as you gain experience youll find theres a vast amount of related info on the web site,
and
without testing you simply guessing
never guess, deal in verified FACTS!
guessing is a waste of time
think logically, isolate and test

get a code reader and a multi meter , pull codes check fuses and get a shop manual for your year corvette the auto parts store books leave out a great deal of info
autowiz said:
So on your FP relay pin D is a drk grn/wht wire and it is power to energize the relay from the ecu. This pin should have power for 2 seconds after you turn the key on and when cranking. Pin E is a red wire that connects the relay to the pump. There is a fuse in between the relay and the pump, it is fuse #20 in your passenger compartment fuse block. Pin E is the output of the relay that is controlled by pin D so it, too should have power for 2 sec when the key is turned on and while cranking. Pin A is Power coming into the relay. This is an orange wire and it goes to the stack of fuse links behind your battery. You should have power at the orange wire pin A all the time. If you do not have power at this orange wire then you might need to replace one of the fuse links behind the battery. And finally pin F is a blk/wht wire and should be connected directly to chassis ground.


Wait, did I say finally?? Well there is one more pin. The cool pin of the fuel pump relay. Pin C. And why is pin C the cool pin? Well because pin C is a red wire that connects directly to the ALDL connector under the dash for easy diagnostics. It goes to pin G of the ALDL connector. It is a red wire on this end also. This wire connects ultimately directly to the fuel pump. So whenever the pump has power, this pin has power. This pin at the ALDL is a great place to begin the diagnostic process for your trouble code.
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 the problem and isolate and test you,ll soon find the answers
its the links and sub-links that easily contain the bulk of the info,
in most of the threads
so skipping them would be to your detriment or loss.

a bit of taking advantage of EXPERIENCED peoples hard won knowledge helps,
I know I found out its a whole lot faster to learn from other peoples experiences, than needing to make your own,MISTAKES and the links posted, provide access ,
its a damn shame many people would rather be set on fire and rolled in broken glass rather than read and take advantage of linked info.
I know I spent 50 years learning from both my own mistakes and occasional successes and researching other successful combos,
even I eventually saw a trend, and the short cut was to do research, rather than relying only on making successes/mistakes on my own.

IF YOUR SIMPLY TRYING TO GET A STOCK TPI CORVETTE ENGINE BACK IN SERVICE AS CHEAPLY AS YOU CAN?
the heads and block surfaces must be very carefully examined for damage or warping issues and if found those issues must be corrected, before any new head gaskets installed, over time steam can and will cut grooves in even cast iron blocks and rather easily in softer aluminum. no head gasket will seal a badly machined or warped head or block

btw if youve managed to blow a head gasket on a 1986-91 TPI corvette with aluminum heads
the heads and block surfaces must be very carefully examined for damage or warping issues and if found those issues must be corrected, before any new head gaskets installed, over time steam can and will cut grooves in even cast iron blocks and rather easily in softer aluminum.

keep in mind coolant must have the anti-freeze ratio set at 50%water 50% antifreeze and be replaced at least every 4 years MAX to retain its anti corrosive additives
fel-hs7733pt9_xl.jpg

fel-hs7733pt9_xl.jpg

the stock 1986-91 tpi head gasket FELPRO HS7733pt9


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
96manual.jpg


think things through, ask questions if you need too

THEY CONTAIN A HUGE AMOUNT OF RELATED INFO
PULL THE TROUBLE CODES
because pre-1996 corvettes are not OBDII code scanner compatible youll need to use the trouble code flasher to get the trouble codes

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, loose electrical connectors, defective sensors, lack of compression, fuel delivery issues ,fuel pressure, vacuum, temperature or electrical issues.

http://www.helminc.com/helm

1996_Corvette.jpg



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

feulpres.jpg

http://www.harborfreight.com/5-in-1-dig ... 98674.html
image_6238.jpg


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

http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/
READ THESE
http://garage.grumpysperformance.co...-the-rabbit-hole-with-alice.10933/#post-66925

http://garage.grumpysperformance.com/index.php?threads/hello-grumpyvette-here.278/

http://garage.grumpysperformance.com/index.php?threads/i-doubt-many-guys-notice-but.4900/


THE LINKS SHOULD HELP

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

http://garage.grumpysperformance.com/index.php?threads/cleaning-a-corvette-tpi-throttle-body.3145/

http://garage.grumpysperformance.co...elay-switch-locations-and-info.728/#post-9217

http://garage.grumpysperformance.co...ouble-shooting-flow-chart-info.596/#post-1200

http://garage.grumpysperformance.co...t1-fuel-system-trouble-shooting.595/#post-782

http://garage.grumpysperformance.com/index.php?threads/l98-start-sequence.330/#post-404

http://garage.grumpysperformance.co...asic-trouble-shooting-on-the-c4.302/#post-367

http://garage.grumpysperformance.com/index.php?threads/tracking-down-an-electrical-drain.8493/

http://garage.grumpysperformance.co...hings-thru-and-verify-each-possibility.11219/

http://garage.grumpysperformance.com/index.php?threads/testing-an-alternator.3222/#post-46703


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.


image_6238.jpg

irtemp.jpg

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
1996_Corvette.jpg



http://garage.grumpysperformance.com/index.php?threads/testing-an-alternator.3222/#post-46703

http://garage.grumpysperformance.com/index.php?threads/is-my-alternator-shot.7808/#post-26803

http://garage.grumpysperformance.com/index.php?threads/long-start-or-crank-time-on-early-c4.16444/

http://garage.grumpysperformance.co...4-started-running-like-crap.10970/#post-48278

http://garage.grumpysperformance.com/index.php?threads/cs-144-troubleshooting.12494/

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

http://garage.grumpysperformance.co...ood-alternator-putting-out-low-voltage.12221/

http://garage.grumpysperformance.com/index.php?threads/battery-or-alternator.10003/#post-43220

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-69239

http://garage.grumpysperformance.com/index.php?threads/electrical-puzzler.13038/#post-67835

http://garage.grumpysperformance.co...questions-can-be-found-here.12892/#post-66934

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772

http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/#post-59136

http://garage.grumpysperformance.co...uys-don-t-look-at-the-clues.11176/#post-50124

http://garage.grumpysperformance.com/index.php?threads/chasing-a-crazy-electrical-glitch.986/

http://garage.grumpysperformance.co...wrong-after-alternator-swap.13580/#post-70168

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-6985

http://garage.grumpysperformance.com/index.php?threads/diagnoseing-tpi-lt1-problems.1241/#post-2648

http://garage.grumpysperformance.co...uel-injector-resistance-reading.606/#post-805




YOUR ALWAYS FREE TO REGISTER AND ASK DETAILED QUESTIONS
 
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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 c4 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

marvel.jpg

MMO is NOT an oil additive!, its simply a rather thin viscosity, high quality, automotive and machine oil,
with a high level of sludge solvent, and friction reducing additives.
that works well at breaking down and holding in suspension micro contaminants ,
so the oil filter can trap and hold them.
its not a miracle cure for anything but it certainly helps keep engine parts cleaner,
and its well documented to help free up sticky moving parts over time

 
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