fjm59vette

Hi to all the C4 Gurus,

My 94 vette has developed a serious problem lately. Seems like when she gets to normal operating temp all of a sudden she starts sputtering, tach goes wild, won't maitain normal idle or accelaration.

I get ASR light and Service engine soon light. Fiirst Time - I disconnected battery got her started and got her home, 2nd time same thing. 3rd time I got a block and just barely got it started again and home.

I pulled the codes and got the following:

H16 DI Fault
H36 Mass Air Flow Burn Off Circuit
H42 EST Circuit
H62 Oil Temp Circuit (High)
H65 Oxygen Sensor Circuit - Rich Exhaust


I suspest some of the code might be the result of the real problem and got thrown.

What do you think is the real problem ?

Best course of action to take in determining issue

I mean it talks about everythinng from MAF sensors/EGR/ICN to ECM as possible probs.

Your advise is greatly appreciated !!!!

Thanks
fjm59Vette

theadmiral94

Clue is 'gets up to temp',

How many miles on the OPTI distributor?

What is 'digital' dash coolant temp when its 'up to temp'?

Suggest checking:

1. battery -- if old or not cannot maintain at least 75% charge (i.e. greater than 12.4 volts), could be the problem as our cars

2. Alternator -- is voltage constant , does dash lights pulse -- if no to either, perhaps its dying.

3. Coil -- heat can sometimes cause these to fail

4. Wires -- coil and spark plugs -- open hood in the dark when up to temp and look for any sparks jumping especially in/around the coil (passenger side front of engine).

5. ECM -- too much heat -- try and wrap with some thing to insulate from engine heat and see if any different?

fjm59vette

Just did the opti last year - Delco Brand. I dont believe its the opti - acting up differently then when opti went south.

Temp Just less then normal last time it died about 170-180 degrees - It normally will get up to between 188-192

New Battery - maybe 6 months old - but I will check charging

Good suggestions

Just for info porpuses - Im getting different error reason for the codes I posted

Autozone

says this

Code 16

Direct ignition system (DIS), fault line circuit or Distributor ignition system (low resolution pulse) or Missing 2x reference circuit or OPTI-Spark ignition timing system (low resolution pulse) or System voltage out of range

Code 36

Ignition system circuit error or Transaxle shift problem - 4T60E Transaxle


Code 42

Electronic Spark Timing (EST) circuit grounded or Ignition Control (IC) circuit grounded or faulty bypass line



Code 62

Cruise vacuum solenoid circuit fault or Engine oil temperature sensor, high temperature indicated or Transaxle gear switch signal circuit fault

Code 65

Oxygen Sensor (02S), right side - rich exhaust indicated or Cruise servo position circuit or Fuel injector circuit low current

STL94LT1

Well you've got both low/high res opti codes (16/36). That usually means the opti is toast.

fjm59vette

I just started it - it ran fine for about 20 minutes, idled & reved perfectly got up to normal operating coolant temps about 188-190 - oil temp got to about 170, the the **** started and she died again. dico'd battery cleared codes -started it - it craped right out.

Pulled codes first got 62 & 65 - then second time 36, 42, 62,65 - no more 16.

RickF

I had similar issues in my 94. Threw a bunch of codes. Don't remember which ones but pointed to Opti. My idle would go high and fluctuate which you don't mention. Tried everything and nothing worked. Decided to change the wires with the Opti being the next (dreaded) step.

When I pulled the wires on the Opti side there was some sort of white powdery corrosion. Cleaned that out as best I could and installed the new wires with dilectric grease.

While putting the camber brace back on I broke the temperature sensor on the front of the engine so I replaced that. IIRC this is the one the ECM uses.

I'll never know which one was my problem. The wires would make sense. However, my problem only occurred at temp (closed loop?) so maybe it was the temp sensor. Either way the car runs like a champ ever since on the original 80K Opti.

Good Luck

jfb

One symptom, the tach going crazy, points to a failure in the ignition module, it supplies the tach pulses and the current pulses to the spark coil. Relatively inexpensive and also failure when hot is common. I'd replace the module as an inexpensive trial.

M. Schumacher

My money's on a computer problem. Too many things going wrong all at once.

theadmiral94

Regarding the codes being different at Autozone (e.g. 36), and remembering their using their little 'code' machine or database, so I would use the Forum/FSM explanation over Autozone (e.g. FSM Book 2, section 6E3-A82 for the DTC 36).

Also, when pulling codes there are different 'modules' (FSM section 8D), and a DTC 16 from the CCM (module 1) has a different meaning than a DTC 16 from the PCM/ECM (module 4), so if the Autozone 'tech' or their machine or database was incorrect or mis-keyed, that might further explain the differences.

Onto the problem -- is there any chance that once the car heats-up that the water pump is leaking (gaskets or weep-hole underneath) and is dripping on the OPTI, causing the problem, then evaporating and allowing the OPTI to function again afterwards...

fjm59vette

No Water Pump Leak

Opti was replaced about 6K miles ago along with water pump

The last set of codes I pulled were

36 DI System fault
42 ICC fault
62 Oil Temp Switch - high temo indicated
65 O2 Sensor Rich

Since I just put the OPTI & Water Pump in 6K miles ago, No water or coolant leaks (I make sure I check that fequently, from last Opti Failure & Replacement), garage kept.

Im kinda leaning to it being the Ignition Control Module or the ECM - given they are OE.

I noticed today when I started it ran for about 5 minutes and the condition started again.
But sh*t started coming on and off like the fan - it was kind a wacky. That never happened with OPti last time.

Also with the Optoi she would just die and you couldnt start it again - it didnt run rough and idle fluctuate?

fjm59vette

I've been reading some manuals and posts, clear my sytem to get new codes, and the only codes that threw were in module 9, they were 62 & 65.

and from what Ive read the codes pertain to the ASR sytem and not the Ignition or Opti.

Since the ASR system can retard Spark and Throttle - it makes sense that it could cause, irratic idle, loping and stalling just like the Opti going south!

Does anyone here have any experiences with a bad or faulty ASR causing erratic idle and engine stalling -then hard starts?

Can the ASR faulting do this?

Help !!!

fueler

I had the same problem a few years ago with my 94 vette. It was the pigtail to the temp sensor in the front of the engine. It would start running bad, would not idle and die. Then it was real difficult to start.

onedef92

Either the PCM's got dementia or the ignition control module (ICM)'s gone ****-up.

FireRoc

In the 94 both the tach and the ASR get their engine RPM signal from the ignition module via the tach filter. (found this out the hard way when we converted our 94 car to the Bailey Engineering LTCC LS1 coil on plug system).

As already suggested, I betting that its its a bad ignition module.

ChrisLT1conv

That is my hunch too.

ChrisLT1conv

In light of reading this. It sounds very plausible. An icm is 80 bucks. I replaced mine when my opti quit troubleshooting. To bad your not closer or I would loan you my old one just to see.

Rag Top

I would check the temp sensor, as others have suggested. I will skip the how, but the wires to mine were damaged. My symptoms were tach jumping, car dying/stalling when warm, and missing. Just make sure the connection is in good condition. The fan coming on and off you mentioned might be a sign. If the computer does not know the correct engine temperature, it cannot control the engine properly. It can't hurt to check.

onedef92

It can't hurt to check.

At this stage in the game, it can't hurt to check anything suspect.

TomDoc27

I have been having he same issue please reply if you found a solution. It first started on a medium road trip. I drove for bout an hour and then it stalled with the tach going nuts. I put some coolant in, restarted after a half hour and it ran for a few minutes and broke down again. I did some research and found out it might be an ASR issue so I waited about an hour, started it and immediately turned the ASR off. It drove flawlessly for 4 hours straight. Same thing happened on he way home. recently however the car wont run for more than 2 minutes or until it gets heated up. then it stalls out with the tach going wild, and a small amount of white steam or smoke coming from the passenger side of the engine block. I replace the injectors, fuel filter and spark plugs so far and the issue persists. please help if you have found a solution. Do I need to get a new asr?

desertmike1

This thread is 2 1/2 years old.. you need to start a new one, and give the year of the car... you'll get plenty of advise