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Discussion Starter #1
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►
 

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Discussion Starter #3
That's what I want to do but my obd2 reader won't communicate with it. Trying to find someone located that will let me take their scanner for a test drive. Someone on another forum mentioned unplugging the o2 sensors and seeing if the problem corrects itself by staying in open loop. Going to try that today.
 

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1995 OBDII ? or the year that could be a mixture ?

Post your location so maybe a member near you can help.
 

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Discussion Starter #5
I'm in VA beach Va. I recall from my dealership days that what I need is a scanner that can read obd1 but has an obd2 adapter. I remember our tech 1 scanner that we used had an adapter. My dealership days were 15 years ago so dont really have the connections anymore.
 

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1986
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Any members near him to help out?

Could always get a cable (or make one) and use the laptop based software to view it
 

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Discussion Starter #7
Well I installed new 02 sensors and let it run for quite a while. No rough idle and no check engine light. The test drive later this evening will let me know 100% but it may be fixed. 🤞
 

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Discussion Starter #9
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.
 
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