A guy I know, not on any forum, has a 93 40th Anniversary Edition. He bought it a few years ago with 20K miles on it. Now it runs fine until it gets warmed up. Then it sputters and will barely keep running. He took it to the dealer and they did diagnostics on it, changed plugs and wires and told him it was fixed. It was not. Still runs like crap when it's warmed up. He thought maybe bad gas or vapor lock. I thought maybe ignition module.
Do any of you guys have any idea what it might be? The "Corvette Expert" at the dealership didn't know.

 

Almost sounds like a bad optispark. But people tend to blame the opti too soon. Could be other things as well. Check the spark plugs to see if any of them are saturated in fuel (bad/stuck injector). Could be anything as simple as the fuel filter. Also have him check the fuel pressure if he is able to.

 

He knows nothing about cars. He took it to a Corvette specialty shop and dealership. Both thought they had it fixed, but it wasn't.

It only runs bad when it's warmed up. When it gets to a certain temp, it starts running really rough. Could a bad optispark be temperature sensitive? When it's cool it runs fine.
Thanks.

 

The symptom you are describing could be the result of one or more different issues.

Had the same issue - would stumble and fall on its face stalling out at warmed up temps.
https://www.corvetteforum.com/forums...ignal-low.html

 

Need to check fuel pressure first.

To answer your last question, yes, a failing optispark can be very temperature sensitive. If he notices his tach bounces and then drops to 0 then it is more than likely the opti. Had it happen a few times. Sad thing is no one really makes quality replacement units anymore.

 

The dealer and Corvette Shop should have checked that. At least I would think so.

 

Thanks guys. I will pass along the information. Hopefully he can get it sorted out.

 

Does the car shut off on him at times, and does it only crank if and when it shuts off?

 

If I'm not mistaken, until (some, the 93s included) these cars run in OPEN-LOOP mode until the coolant temp gets to aprox 160ºF, and then switching to CLOSED-LOOP.

While in open-loop mode, the fuel is metered according to a separate table, independent of O2 readings. But, when switching to closed-loop, then the O2s are considered in the AF mix. Until that happens, everything runs just fine: no codes either. But, as was the case with my 95 LT1, soon as it went closed loop after warming up to temp, it would run like crap.

I too took it to a dealer to fix. But, when I picked up the car, the note on the work order said, "No problem found". Yeah, well, before I got it home (45 minute drive) it was running like crap (and a friend that was following me home called me on my cell phone to tell me the right side exhaust was pouring black smoke!).

In my case, the problem was intermittent to boot: sometimes would act up and sometimes would run great all day. I figured that was the case w/ the dealer too, so I bought my first scanner that had the ability to record "events" and save them to be downloaded (on a PC) later.

Long story short, it was a funky O2 sensor that wuz internally shorting out, indicating an extreme LEAN condition (whereupon the computer was compensating by commanding the injectors on that side to dump buckets of fuel on that side of the motor to correct the lean indication!).

So...your symptoms are like "dejavu all over again" (to quote Yogi Berra). A scanner might unlock some surprises too. (It gave me no small pleasure to diagnose the problem and fix it. Then I presented the dealership's manager with my printout showing the problem printout, and I got my money for the "no problem found" refunded.

 

time it, consistently 15 minutes troubles start. check ECU

 

Like I said, the guy is not mechanical, knows nothing about cars, took it to a dealer and Corvette shop and they said it was OK. Nothing showed up on diagnostics.

 

Ask him if he's washed the engine lately.

 

I doubt if he has ever opened the hood.

 

Fuel pressure check.....when was the fuel filter replaced last? Then I would search for vacuum leaks......there are plenty of places for that to occur. Then test and check the ICM , ignition control module when HOT. Good chance its going bad. Opti distributor next, I very highly doubt anything is wrong with the ECM.

 

I agree. Even though ECM's go bad once in a while, it is NOT common for them to do so.

Hey Ozz! Your the guy with the youtube videos! This is franco!

 

I sure am Franco. :-) I guess I can't hide to well? lol Take it easy -Ozz

 

Would that cause it to run bad when warm and run good after it's cooled off?
I would think the dealership would have checked fuel pressure when he brought it in.

 

Coil

 

I thought about that. Something else to look at.