I have a 1992 Corvette, LT1, M6 completely stock. This problem started after my vette had to be in a non-heated/non-insulated garage for two weeks while my main garage floor was getting refinished. During those two weeks temps ranged from 0 degrees to 60 degrees.

On first start up, the car runs pretty normal, although I never get on it too much until it warms up. After 4-5 minutes of driving, it seems like my car is starving for fuel (think being in too low of a gear/stumbling) until it hits about 3,000 RPM. After 3,000 RPM it runs like a champ and like there isn't a problem. Also if I just drive it normal without getting on it, it runs just fine. Seems to only be a problem when I go to get on it at about 2,000 RPM. I really like to do 15-40 mph runs when on the highway, and at about 15 mph in 2nd gear I'm about 1,800 or so RPM and it studders until I hit 3,000 RPM, then runs out like normal. Also, the car idles a little rougher than normal, but it just surges from 750-1,000 RPM and I never get the feeling it's going to die. While idling, if I go to rev it up, it kinda studders at first then goes on like normal.

I've done some searches regarding the opti and so forth, and most of those threads seem to have the stumbling problem all the way through the RPM ranges when it warms up. Which has me confused.

So I'm coming to the experts. Do you guys/gals think this is a fuel issue or an opti issue?

Also going to apologize in advance, I don't really have a lot of mechanical knowledge, so I probably would have to just have a mechanic check the fuel pressure and all that information. I also apologize if it seems like a rambling of thoughts, I wanted to provide as much information as possible.

 

It is possible that it is the Opti but it can't hurt to check the fuel pressure. How old is the coil? The coil on those engines soak up a lot of heat which affects their lifespan. Thankfully they are relatively easy to get at.

Does the car throw any codes? Normally if the ICM is bad it throws a code.

Keep us posted.

 

Is it the original opti?
How many miles on the opti?
Have you pressure washed the front of the engine at any time?

Other than that see if you can find an old school honest mechainc (probably not the dealership - car is too old). Have them check the wiring harness from the opti to the ECM connector on the passenger side of the intake. Have him check the ICM and coil (if they are original it would probably be less expensive to just replace them)

Why did I say not the dealership because the car is too old:
Any "new" mechanic was probably trained on C5 & C6 and would not have shop manuals for your car. Now if you luck out and find a Corvette mechanic at a dealership that has been doing it for 25+ years then you can take it there. I know of one in the ATL, he didn't even take my copies of the shop manual out of the car.

 

As far as how old the Opti is, I honestly have no clue. My car has is right around 118k miles. When I purchased the car he had an opti that he bought as a spare, so I'm guessing that it hasn't been replaced recently.

Nope, I've never pressure washed the front of the engine.

Thanks for the help guys. I think I'm just going to bring it to my mechanic and have him do all the testing. Then he can determine if it's a fuel issue, or something else.

 

Just thought I'd give an update.

I got the car to my mechanic and during the diagnostics he checked the spark plugs and wires. He said the spark plugs absolutely needed to be replaced (very burnt looking). While in the process of changing out the spark plug wires, he noticed the opti-spark connections were all corroded and in bad shape.

So after taking off my old opti, he showed me wear it was actually sparking across the different connections causing mis-fires and frying the connectors.

So in the end the opti-spark was the culprit. But the good news is that while he was in there he put a brand new opti, brand new water pump (both are new and not re-manufactured ones), Taylor spark plug wires and NGK spark plugs. Also got a fuel pressure test and everything checked out great.

I couldn't be happier as my car runs better than when I first bought it 6 months ago. Ones of these days though, I really want to learn to work on this car. I can change alternators and stuff like that, but just don't have the confidence to get into the opti-spark stuff.

Thanks again to everybody for your help!