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I am the third owner of a '92 convertible, it sat for 10+ years before the 2nd owner sold it to me, the Opti-spark had failed on it. I replaced the Opti-spark unit with an MSD unit, flushed the fuel, replaced the radiator and fuel pump and filter and got it on the road and it has run nicely for years. A couple times late last year the car would die intermittently, going down the highway the engine would just stop and I would pull over and after a few minutes it would start again. I just got it out today and it did the same thing, started up fine, ran great for 10 minutes, then died while doing 65. Sat along the road for 2 minutes and it fired back up. It always turns over without issue, and when it runs it runs fine, but when it is out of commission it will not start but everything else is normal. I don't think it is the Opti-spark unit, it seems like it could be something with the fuel pump, maybe a bad connection somewhere? Anything else I should look at?
dies when hot and runs when cooled sounds like heat soak, parts failing when they heat up. First want to ask if you have read for engine code, please post if so. My first guess is going to be either the coil or the ignition control module. Since both are mounted together on the side of the cylinder head they get warm. If that is the issue don't forget the thermal paste when reassemble, very important. Also clean that bracket up that holds them. If that is not it....well post those codes if you have them.
Well it seems it is not the ignition control module. I ordered one along with the coil and installed the new ICM tonight (using the right amount of thermal paste!), took it for a test drive and it died in the exact same spot it died last time and was subsequently intermittent as it had been before, so I will read the codes and plan on swapping out the coil as well.
92 and 93 corvette ECMs have known solder problems on their circuit boards causing problems like you are having. You can send your ECM to SIA Electronics and they can test it and reflow the solder on your circuit board if needed.
Knowing which, and the combination of codes is important.
When it dies does the tachometer go to zero? Are there other lights on the DIC such as SVC ASR? (Both of these together, and a Code 1.41 will be the ICM.)
You can carry a jumper with you and when it dies and won't restart, querie the onboard diagnostics with A&G. If 1. H16 is present, clear it. Crank it. If it still won't fire, querie the codes again. If H16 is back, it is an opti problem. Note: ECM Code 16 will always show as a History code, never as a Current even if 16 is the problem. The two opti codes 16 and 36 compare themselves to the other; if one is missing, the code is set. The engine has to be running for this comparison to be "Current". The test is to clear the H16, and if it is right back, it is the opti.
Knowing which, and the combination of codes is important.
When it dies does the tachometer go to zero? Are there other lights on the DIC such as SVC ASR? (Both of these together, and a Code 1.41 will be the ICM.)
You can carry a jumper with you and when it dies and won't restart, querie the onboard diagnostics with A&G. If 1. H16 is present, clear it. Crank it. If it still won't fire, querie the codes again. If H16 is back, it is an opti problem. Note: ECM Code 16 will always show as a History code, never as a Current even if 16 is the problem. The two opti codes 16 and 36 compare themselves to the other; if one is missing, the code is set. The engine has to be running for this comparison to be "Current". The test is to clear the H16, and if it is right back, it is the opti.
Thanks for the feedback. When it dies the tach goes to zero, and it can die at 75mph or sitting in park. Once it dies it takes 5 to 15 minutes and it fires back up. I don't think it is the opti-spark, as on the 2 occasions those have died, it of course never starts back up. I will see what SIA electronics says when they get the ECM and let you know what they find.
I had an MSD unit fail after just 1 year on a 93 Z28 I used to have
Are you referring to an MSD coil or opti-spark? I replaced the original failed opti-spark with an MSD setup and that only lasted a year or two, out of spite I bought the cheapest Chinese opti-spark I could find and that has held up thus far.
I work for Hitachi so I thought I would replace the coil with one from Hitachi, but it seems that was not the fix...
Are you referring to an MSD coil or opti-spark? I replaced the original failed opti-spark with an MSD setup and that only lasted a year or two, out of spite I bought the cheapest Chinese opti-spark I could find and that has held up thus far.
I work for Hitachi so I thought I would replace the coil with one from Hitachi, but it seems that was not the fix...
No I replaced the whole Opti spark unit. I was a bit disappointed that it only lasted a year.
SIA will most likely reflow the solder joints that go bad and test it and ship it back. So my 93 did this exact thing, 60 mph just shut off like I turned the key off. After I had to get towed a couple times I let it warm up in my driveway one day until it died. Then I put a ice pack on the ECM box and closed the hood for 10 minutes. When back out and it started right up, then when it got hot again died. SIA reflowed mine, but when I got it back it was still doing it with less frequency. So I sent it back under warrantee and they reflowed again, but while I was waiting a week or two I found and already repaired one for a good price and grabbed it as a backup. When the SIA one came back I swapped my PROM into the one I bought. Since I have been put 3-4k miles on it and never had a hiccup. I still have my original SIA repaired one as a backup in case. I also did a VATs bypass as my security kept shutting it down when the wires broke inside my ignition switch for the VATs resistor.
Throwing this in here because I have a degree in microelectronics. Circuit boards built in the C4 corvette years have much poorer quality solid state devices on them (resistors, diodes, capacitors, etc) than current tech, and they are more prone to heat. The ECM sounds like it may have a fail-safe circuit to protect from heat (not sure, I am still learning C4 stuff, but the possibility is there), and thus shutting off the ECM in an over-temp scenario. If not then it's likely just to much heat on the board in general, which would also cause a shut-off scenario. If you could keep the ECM cooler/ventilated better, you would see positive results.
Just got a call from SIA, they said the ECM checked out fine and they could not get it to fail, they also said it looked like it had previously been re-flowed, which I am skeptical of, but I guess it could have happened, so where to look next?
Revisit Post #8. Carry the jumper. When it dies, look for Module 1, H16. If it is there, clear it. (Module 1.7, cleared indicated by "- - - "). Crank it and if it won't fire, check the codes again. If H16 is back, it's the MSD Opti. (MSD Optis have a not-so-good reputation on here. Lots of peeps report disappointment with MSD optis.)
Revisit Post #8. Carry the jumper. When it dies, look for Module 1, H16. If it is there, clear it. (Module 1.7, cleared indicated by "- - - "). Crank it and if it won't fire, check the codes again. If H16 is back, it's the MSD Opti. (MSD Optis have a not-so-good reputation on here. Lots of peeps report disappointment with MSD optis.)
I will do this when I get the ECM back and installed. I thought once the Opti-spark died, it was dead, that they were not intermittent, but perhaps that is not the case. As I mentioned, I got the car because it had a dead opti-spark, put in the MSD unit, it ran for a few thousand miles, then died, now I have a non-GM and non-MSD replacement.
I have a '92 base model doing the exact same thing right now. Module 4 DTC's would change from Code 41 (EST circuit fault) to Code 43 (ESC circuit fault). Like you, I sent the ECM to SIA and had the board reflowed. The tech there said they found some cold solder joints and when I reinstalled it, I still have the same problem. Today I was able to follow the FSM troubleshooting chart A-3 for the crank/no start, which led me to Chart C-4 (Opti-Spark ignition system check) which led to "Faulty distributor connection or faulty distributor". I wasn't getting a signal on the low resolution line coming from the opti, which can prevent the engine from running. I know you said you don't think it's the opti, but I didn't either. Mine is only a little over a year old. It's a fairly easy check if you follow the FSM. Just wanted to share my experience in case it helps. These electrical gremlins are frustrating.
92 dies intermittently
