TripleWhiteLT1

I have a '92 Corvette with only 59k miles on it. I believe it is completely original under the hood, including the Optispark system. It has an automatic transmission. I just got this Corvette, and in the span of less than 500 miles this problem has surfaced several times.

The engine runs fine, very smooth with plenty of power, but will randomly stall while I am driving. It has stalled under multiple different circumstances(freeway, around town, etc). I will be driving along, and it will instantly die, as if someone turned the ignition off - No sputter or stumble, just shuts off. I have noticed that my tachometer needle will bounce around randomly immediately after stalling, usually for a few seconds, before falling to 0RPM.

At one point, I was running it with the hood open and peeking around to see if I could see anything obvious, and it died while I was standing there. No stumble, just shut off as if the key was turned off. For several seconds afterward I could hear what sounded like the injectors and possibly some relays cycling on and off rapidly under the hood, while my friend in the car said the tach was bouncing around the whole while. I went to the back of the car and listened and could hear the fuel pump still running. I then shut the ignition off.

It always restarts after stalling, though sometimes I have to open the throttle slightly to clear the flood condition from the injectors cycling before it will restart. I have never seen the check engine light come on while it's running, nor has it ever given me any other indication of problem except for the stalling. It has never done it with the engine cold, only when fully warmed up, though it does not always do it when warm. The first time it happened was after perhaps 20 minutes of driving, but the next day I drove it more than 170 miles and it didn't stall once. I parked it several days, then drove it less than ten miles before it started stalling, and it probably stalled on me 20 times before I made it to my destination. I would let it sit for a few minutes, then make it perhaps two miles, where it would die again. Sometimes less distance. However, two hours later(and later in the evening when it was cooler outside), I drove the entire 55 mile trip back home and it didn't stall once.

I restore classic cars for a living, but I get lost when working with these computer controlled cars. I have heard of many issues with the Optispark in this, and I can't help but wonder if this is what they typically do when they go bad. I'd like to start troubleshooting this problem, but I'm not entirely sure where to begin. How does one go about testing the various electronic components in this system? Any insight? Thanks in advance.

jaa1992

Could be ICM or Coil (or both)
Also check for codes, in The FSM there is a procedure for connecting a couple of the ALDL pins together and reading codes on the spedometer.

syco_cop

I would have to agree with jaa on the ignition module. Because the module is what tells the ecm to run the fuel pump and injectors. If the injectors and fuel pump are running after the engine died it is probably because the ignition module is sending a false signal.

Also ignition modules do weird things when they get old and hot, and since you seem to be fine in cooler temps I would suspect the module.

TripleWhiteLT1

Thanks to both of you for the input. I am assuming that FSM stands for Factory Service Manual? I'll have a look in there for the procedure you describe.

I had suspected that it was some sort of electronic problem like what you describe with the ignition module, so I will dig deeper and let you know when I find out what it is. Thanks!

redvetttes

Click on the top left hand link
then on the 3nd from the bottom

http://temp.corvetteforum.net/c4/vader86/

armysnipe

I had a similiar experience with my 93 LT-1 (Auto). I finally tapped on the ECM while the car was running and the car would die. So, I removed my ECM and sent it to K&B Special Products for repair. If needed thier website is www.kandbcorvetteproducts.com. This is too easy not to try and it only takes a few seconds. Just don't bang too hard on your ECM. Hope this helps.

pr0zac

from what i have seen if your tach is messing up its usually a coil.

Scotsman

quick question. Do the fans come on when you restart after it stalls?

redvetttes

If ac is on yes or
over 220 yes

TripleWhiteLT1

That is a good question, and I will have to check and hopefully duplicate the problem, as I don't remember definitively. My recollection is that they did sometimes, but not others. I never paid any particular mind, as the fan is supposed to come on when the fan thermostat reaches a certain temp anyway, which it may have. But I will see if I can duplicate it and check.

Why do you ask? What will this tell me, one way or the other?

TripleWhiteLT1

I will try this, though for what it's worth I did jiggle it at one point while it was running to see if there was possibly a loose wire connection - Though I didn't tap on it.

Railroadman

You will often hear a piece of good advice here - locate the problem, don't just throw parts at it. I agree. However, since the car is new to you, and you don't know how old various parts are, you can replace the coil just for peace of mind. They go for ballpark $40 and even if that's not the problem you will now have a new coil you can (hopefully) count on for a long time. Keep records of what you replace - date, mileage etc - so you can check back.

imaruby

Same thing happened to my '93.Eventually it will happen again at shorter intervals.
Sounds like the opti-spark.If you get codes 16 and/or 36 its the opti-spark for sure.
Keep waving,Ray

FOXX

Fuseable link? Bad ground somewhere? Wiggling wires around sometimes reveals all.

TripleWhiteLT1

Is there something more than just a coil of wire in these coils for these cars? It has been my experience over the years that ignition coils themselves all but never go bad. Are these coils somehow more complex than the coils of old?

jimmymack

FWIW, friend had a similar issue, 94 w/about 50K on clock. Dealer replaced opti, coil and injectors (classic case of throwing parts at problem )...still had issue, turned out to be bad, original fuel filter. Spent $1500 when it could have been fixed for about $20. Has run fine for last 3 years.

Not saying it's your issue.

If you don't have any maint. history on car, pull codes as suggested and go from there. Lot's of people here to help

redvetttes

Over the years. Yes
Now were talking made in china

Scotsman

The reason I asked about the fans :

Had a problem much like yours last spring. Car would run fine at start up, then would stall in the driveway while warming up. I could restart just fine, but when I did, both fans came on and would stay on. I had other members tell me this was called "safe mode" or "limp home mode". I'm not 100% certain what else happens in "safe mode" other than the computer sees something wrong, and takes precautions. Over a period of time, as another person described, the time between start up and stall out got shorter. One day, it wouldn't restart.

Long story short, being new to the LT1, I started down the list of possibles. Replaced coil first, same problem. Then had computer rebuilt when things were pointing that direction, same problem.

Eventually after much cursing, adult beverage consumption, and cash, I replaced the Opti...problem solved.

For redvetttes: I'm perfectly aware of when the fans engage under normal circumstances, I was inquiring of the OP additional information relating to his problem. Thanks for the clairification though.

Now, I'm not above thinking that possibly it was a combination of several items causing the problem, but the opti replacement stopped it.

By the way, I experienced the same "tach jumping around" symptom you have. I'm not saying you have the same problem, but we're both driving '92 6 speeds, and what you're describing sounds a lot like what I experienced.

Best of luck, I hope this helps a bit.

TripleWhiteLT1

Well, I finally had a chance to mess with it today, and I pulled the following codes:

16
36
42

My research so far seems to indicate that I can narrow it down between either the Optispark unit or the Ignition Control Module. I'm going to reset the computer to erase these codes, then drive it until it stalls again, and check the codes one more time to be sure.

I have checked all wiring connections, and they all look good, with clean contacts, and absolutely no indication of intermittent connection.

I have heard it said many times that these Optispark units are problematic. Assuming I do end up having to replace it, what does an Optispark typically go for? I went in to my local parts store, and the fellow there had no idea what it was, and found nothing in his computer for this car except the Ignition Control Module. Where would I typically buy the Optispark unit for this car if I need to pick one up?

Thanks!

Scotsman

I ordered the last one I installed from Summit Racing...was their "cheap" model, I think for about $250 or so. Has worked fine for a year now. I know a lot of guys only use the GM part, which would seem like a good thing to me if they didn't cost upwards of $600 each.........I have a family, and that much money would probably cause my wife to blow several gaskets, and thereby lower my chances at overall happiness.

Good luck man, opti replacement is kind of fun once you get past the cursing and into the drinking.