I have a 1990 C4 Corvette Base model with automatic transmission that is having a drivability/safety issue. I don’t get any codes or service lights. I can replicate the issue, which occurs after allowing the car to sit and idle after approximately 15 minutes. The car will surge, stutter and die when I accelerate from the stopped position. If I rev the engine a few times, the engine will return to normal running. I have not been able to find the problem. There doesn’t seem to be any issue with the car until I am stopped in traffic and must let the car sit and idle for an extended period. It then becomes a real safety issue. The car has less than 100K miles on it. I am the second owner and I put about 40K of those miles on the car. I was hoping someone could provide advice on what to look for. Appreciate the help.

 

It sounds like it happens when it hits closed loop operation if it’s after about 15 minutes. So I’d say a sensor somewhere isn’t happy. I know that’s vague, but you could try disconnecting some sensors to trigger “limp mode” where it just runs off base tuning.

Previous experiences on 90s GM products with their current age, I’d 100% check your fuel pressure to test injectors, regulator and pump. Then I’d check your intake sensors (MAP, IAC, etc). Plus your EGR solenoid. You can try disconnecting some of these one at a time, and see how it runs. If these reading are omitted and the computer uses base values for these, you may be able to find your culprit. The engine should run better or worse, of course if it runs better you may have found something that can help. I’ll preface this with on some sensors, this can be finicky. My 93 blazer had a MAP sensor that would let the engine run fine for about 15-30 minutes, then stumble and die. If I unplugged the MAP it would run even worse. It was disguised as a bad sensor that would test fine, but randomly would go haywire.

This of course is all short of buying a scanner tool to see what your car is really doing. I haven’t been able to justify buying one, I just use some troubleshooting things I’ve read online

My 87 had a stumble like that with similar symptoms, but it was the MAF sensor, which unfortunately doesn’t apply to a 90 since it runs off the MAP, engine temp, and intake air temp I think. (Someone correct me if I’m wrong on that). So maybe check those and see if you get any improvements. I bet someone has had this exact issue and will be able to provide you the exact thing that worked for them.

Best of luck!

 

As you can reproduce the problem, you can test and diagnose the problem.
If you don't have a FSM get a set. Don't waste money on Chilton or Haynes or any of those sorts of "repair" manuals.
To me with the fact that you can "rev" it out says it's some kind of fuel load or air intake issue.
I would start with testing fuel pressure and injectors. Fuel pressure should be 41 to 47 psi with the engine off and the key on. Using a test light make sure each injector is firing when it should. Disconnect all the injector plugs. Engine off, ignition on, connect the test light to the positive battery terminal and probe the striped wire. The test light should not illuminate.
If fuel pressure is correct and injectors are firing and closing a they should I would move to testing the tps and air related sensors.
Using a multimeter test voltage at the connector. Voltage varies by sensor. The fsm will guide you through that. You can find values for each on the forms as well.
Let us know your progression.

 

Why do you let idle for 15 minutes?