So a couple weeks ago I picked up a 1995 LT1 C4 Corvette. 137000 miles automatic. Completely stock. Test drove it and it ran great. Drove it a couple days and everything was great. Once getting it home I was cleaning it up and cleaned the engine. Yes i now know not to get the optispark wet. The next time I drove the car I noticed the idle was a bit rough, throttle response was a little lacking but I could accelerate or power brake it and it would run fine. At times it would sputter in the upper rpm range. Kept the car in a heated garage for almost a week to try to dry it out. Didn't help. So over the last week I have replaced the optispark, optispark harness, plugs, wires, coil, ignition module, iat sensor, map sensor, and maf sensor. Took it for a test drive today and it's still not right. So here is how it acts. Cold start and it fires right up, idles smooth. After it warms up a bit it starts to idle rough. Acceleration is normal up to about 3200. From 3200 to 4200 it feels like it's running on 4 cylinders but not like a typical misfire from a bad plug or plug wire. After 4200 it puts you in the seat. After driving around for 10 minutes it's fine. No rough idle, no hesitation, no nothing. Can launch the car and run all the way through 3rd with no issues. Pull back into my neighborhood, get it the driveway, starts idling rough. Prior to changing anything I could be sitting at a light, running rough. Then all of a sudden the check engine light comes on and it smooths out. Check engine light goes off and idles rough again. Checked codes by jumping the pins and no codes. Ever. Since replacing everything the check engine light hasn't come on but once after my test drive but here again, no codes. I'm stumped. Anything anyone can offer would be appreciated. I'm about ready to start ordering carb swap parts. Thanks► Show Full Signature

 

Unplug the O2's and see what happens after it warms up.

 

I'll try that tomorrow, what is your thought process if it drives ok? Or I guess the question is if I disconnect them should it run normal if that is the issue?

 

You are forcing the PCM to stay in open loop if you unplug the O2's. If the engine runs good then there is a high possibility your O2's are bad. The PCM stays in open loop for a certain period of time before it relies on data from the O2's after the engine starts to warm up.
Before going too far into this, is there a check engine light right now?

 

Check engine light comes on sometimes but doesn't stay on and when I pull codes I get nothing.

 

Forgot to mention when it is running rough it smells like it's running rich as well.

 

You can't get trouble codes by shorting pins. You need to connect a scanner.

 

on 95 corvettes you can jump pin 4 and 12 and use the buttons on the dash to not only pull codes but clear them and cycle through various tests.

 

...ah you might want to download scan9495 and see wtf the code is

IDK how you "cleaned" your engine...but if it involved water don't do that. If your old Opti was a real AC Delco I hope you still have it

What brand of "new" opti did you get?

CEL comes on for a reason...you need to confirm why by using scan software

 

I picked up a summit brand one. Seemed to have the best reviews from what I read other than the ac delco one. Drove the car about an hour ago with the 02 sensors unplugged and it drove flawlessly. Of course the check engine light came in after awhile but that's a given. Waiting for it to cool down now and then I'm going to install 2 new 02 sensors and see what happens.

 

Well after installing the o2 sensors and a 2 hour test drive it's fixed. Drives flawlessly. Thanks for all the input. Really appreciate it.