logically think things thru and verify each possibility

[Grumpy]

logically think things thru and verify each possibility , one of the local guys stopped by with his 1996 corvette, His complaint was that it had and intermittent ignition miss he was having a difficult time locating.
so I pull trouble codes and it says that were having ignition miss fire as expected, I got out my old out of date now code scanner, and IR thermometer,
http://www.professionalequipment.com/xq/ASP/ProductID.3461/id.22/subID.177/qx/default.htm

AutoXray EZ-Scan 6000 and its shows two plugs are causing 99% of the miss fires, #4, and #6 , looking in the shop manual,a quick check with the IR gun shows those cylinders running much cooler at about 250F vs 470F on the other 6 exhaust ports

I noticed something about those two cylinders , they are positioned on the opti-ignition side by side, so I asked if there had been any repair or upgrade work done recently and found that the water pump had been recently replaced, so with that info and after checking the ignition wire connections on the plug ends were good I went and put the car up on the lift and not totally unexpectedly found the #4, and #6 plug wire connections on the opti-crap ignition were loose. they must of gotten loose during the water pump replacement process, and after driving the car the connections got even looser over time. see a bit of logical progression , in tracking down the cause led me too the likely cause.

.lets start with a break-down of the OBDII fault code
1. the first character identifies the related system
P=power train
B=body
C=chassis
U= unspecified
2. the second character identifies if the fault code, is genetic or manufacturer specific. a generic code is the same on all OBDII vehicles, regardless of manufacturer
..a manufacturer-specific code is used by only that car maker
0=generic
1= manufacturer specific.
3.the third character denotes the specific system
1=emissions/fuel-air
2=injector circuit
3=ignition or missfire
4=emission control
5=vehical speed and idle control
6=computer and out put circuit
7= transmission
8=transmission control
the fourth and fifth digit relate to the area where the fault/trouble occurs
example code p0303
p==power train
0==generic
3=missfire
the last two 03 indicate cylinder # 3 is miss firing

p0301=cylinder #1
p0302=cylinder #2
p0303=cylinder #3
p0304=cylinder #4
p0305=cylinder #5
p0306=cylinder #6
p0307=cylinder #7
p0308=cylinder #8

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

http://garage.grumpysperformance.com/index.php?threads/basic-trouble-shooting-on-the-c4.302/

http://garage.grumpysperformance.com/index.php?threads/efi-and-scan-tool-software-links.469/

 

[Grumpy]

http://tech.corvettecentral.com/2011/01/c4-diagnostic-trouble-codes/

Re: C4 sensor info

you really need a old computer, an ADL cable and software to read the info and of course YOU NEED 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, loose electrical connectors, defective sensors, lack of compression, fuel delivery issues ,fuel pressure, vacuum, temperature or electrical issues.

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.

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.

without pulling trouble codes and testing your simply guessing at best,
break the issue down into separate issues,
check ignition strength and timing,and voltage
check fuel supply/delivery pressure and volume
check cam timing and cylinder compression.
check valve train control and valve adjustment
check firing order and spark plug gap
check the valve lift, and for work lobes
check for vacuum leaks
adjust your iac and tps
check your exhaust back
pressure
verify sensors correct function

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

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

the correct matching SHOP MANUAL
TIMING LIGHT
IR TEMP GUN
VACUUM GAUGE
MULTI METER
FUEL PRESSURE GAUGE
COMPRESSION TEST GAUGE

keep in mind the basics you need to verify the fuel pressure is at about 40 psi if your dealing with a C4 corvette,
you should NOT have significant exhaust back pressure, clogged catalytic converters,
are a common problem on older c4 corvettes,
verify the fuses are not blown, the trouble codes do not show any problems,
all electrical grounds are reading good,
verify theres at least 14.5 volts at the battery while its running, so you know the alternator functions,
and all the injectors are functional with a noid light,
all cylinders should read within 10% and show about 150 psi or greater.,
on a compression test, verify the firing order,
set the spark plug gaps at .045 ,
and verify all the listed sensor values,
verify the cam lobes are not worn, verify you have at least 10 psi of oil pressure per 1000 rpm.verify theres no vacuum leaks

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

https://www.harborfreight.com/11-piece-noid-light-and-iac-tester-set-97959.html

https://www.jegs.com/i/JEGS/555/W89...MIoLGlpLnz3gIVDFYNCh36aAK4EAQYAiABEgKTIvD_BwE

viewtopic.php?f=55&t=109

you might have clogged catalytic converters, the ignition timing may be way off, you might have a worn out cam, the fuel pump may be defective, some injector(s) may be defective,check the alternator out-put check the fuel rail pressure use a noid light on the injector wiring, check the fuses,
Ive found that the one most commonly over looked in my experience is that the stock exhaust system, is highly restrictive, especially if the catalytic converters are partly plugged and the stock fuel delivery system is not adequate,for the potential power, the heads and intake, allowable air flow potential, are all restrictive, and the stock cam timing and lift is already near max as it was designed to produce about 260 hp,and operate at under 5700 rpm, if you try too add an additional 100-200 hp, and 1000 rpm-2000 rpm to the engines power band, and too the engines output youll quickly find this to be a factor.
I've also occasionally seen guys, improperly index or install a cam without degreeing it in correctly and thus have power band limitations.
Id suggest you buy a factory shop manual, multi meter and a timing light, fuel pressure and vacuum gauge and start checking.

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.

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

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

http://garage.grumpysperformance.co...ng-high-flow-cats-on-exhaust.8401/#post-29318

http://garage.grumpysperformance.co...s-cause-a-bad-idle-in-drive.14203/#post-72114

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

http://garage.grumpysperformance.co...le-shooting-flow-chart-info.11536/#post-71845

http://garage.grumpysperformance.co...ittent-cylinder-miss-problem.9478/#post-57225

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

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

http://garage.grumpysperformance.co...-you-failed-emmision-testing.3522/#post-52999

http://garage.grumpysperformance.co...and-verify-each-possibility.11219/#post-50643

http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46303

http://garage.grumpysperformance.com/index.php?threads/1991-c4-runs-like-crap.10616/#post-45635