Could use some expert help. I have an idea of what I am going to have to do but I want an un altered opinion. Here is goes.
1995 Corvette LT1, 137,000 miles, well taken care of. Car has run great up until yesterday. Was going through the car, checking fluids, looking it over, etc. Decided to degrease the engine a bit. Sprayed it off and fired it up to dry everything out. Ran fine. Let it sit for a couple hours and took it for a ride. After about 10 minutes of driving I noticed it idling extremely rough. As if it has a cam. Take off from the light and it drives as if nothing is wrong. Floor it and it takes off with no hesitation. Stop at the next light, idles rough, and then the check engine light comes on. When the check engine light comes on it smoothed out and idled fine. Take off from the light, everything is fine. Check engine light goes out, stop at the next light, idles rough. This scenario repeats. So I parked it inside with a heater all night thinking something got wet. Pulled codes this morning and all I got was a history 23 for iat. Checked the iat and it checked fine. Cleared the code. That was the only code stored. Just went and drove it again and same issue. This time however it never stopped doing it and this time the check engine light has yet to come on. And ideas would be greatly appreciated.

 

So decided today to replace the iat sensor since there was a history code for it. Didn't help one bit. At one point the check engine light came on and it ran fine. Pulled over, turned the key off, installed my jumper wire, turned the key on, and no codes at all. Started it back up and continued to have rough idle with no cel. I've also noticed that it smells like it's running very rich. I assume when the Cel comes on it is going into some sort of predetermined mode and not using whatever sensor is bad to keep everything running. And ideas would be appreciated. I'm almost ready to start my parts list for a carb and cam swap. Thanks

 

FWIW, I recently completed an upgrade to Dewitts radiator on my 95. Did water pump, intake manifold gasket, new optispark (got one of the Dynaspark units), plugs, wires, the works. Car was running fine right until the mile or so of the last drive before getting started with the work.. started idling rough, something clearly wrong (No codes though). One of the distributor rotor screws had completely come out and was just rattling around in there. Now that it is all back together, runs smooth as ever and also much better across all RPM ranges. Didn’t realize it before, but I bet those rotor screws had been loose for a while and one finally fell out right on time..

Can’t say this is definitely it or not for you, just sharing my experience.

 

Optispark is what I'm leaning towards but just wanted some opinions before sinking the time and money into it. Not saying it's not possible but all the cases of a wet optispark that I was able to find people complained that it ran rough through the whole rpm range and some even stalled. As long as I've been turning wrenches this has to be the first vehicle I've ever dealt with that obviously has an issue, CEL comes on, and when checked immediately there are no codes.

 

So I've had the car inside, with the heat on, trying to dry it out. Yesterday put known good maf and map sensors on it but no change. Normally it doesn't start running rough until it gets up to about 190. Just started it this evening and at 123 the check engine light came on, fans came on, doesn't feel rough at idle, and it has never felt rough if I power brake it. Throttle response has always been good as well. Got up to 180, check engine light went off and rough idle again. Now it is at 190, rough idle like a cam, bo check engine light, running rich, and a little sputter when I hit the gas. Turn the car off, check codes, no codes. Anybody else want to chime in. Thanks

 

You more than likely wet the Optispark. May as well do the water pump and all associated seals. Problem is, the newer Optispark units are not as good as the GM originals. From what I understand, its getting hard to find an OEM unit too.You might be able to take the cap off the Opti and dry it all out and reassemble...

 

Optispark is definitely what I'm leaning towards. Actually just ordered a summit optispark, coil, wires, plugs, and gaskets. Previous owner put a water pump on it a month ago. I do plan on threading the weep hole on the pump to allow me to install a fitting and hose to route it around the optispark. From what I can see other than the delco ones the summit and jegs ones tend to be the most reliable for the money. Thanks for the input.

 

Now the car has a brand new optispark,plug wires, plugs, map sensor, maf sensor, iat sensor, ignition module, and coil. At times idles rough, and sputters between 3200 rpm and 4200 rpm. Just got back from test driving it. Problem was there leaving my neighborhood. After 5 minutes of driving it went away. Drove around for 30 minutes and didn't act up one time. Pull back in my neighborhood and in the driveway. Running rough again. No check engine light at all during the test drive. I've been turning wrenches 30 years and I'm at a loss.

 

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.

 

I'm wondering if you took any precautions whatsoever to protect the optispark area when you degreased and rinsed off the engine. If you just sprayed degreaser and water everywhere, even from just a straight down 90 degree angle, this caused your unfortunate frustrating chain of events. Self inflicted engine issues are the worst!

 

glad you got it fixed, That would have drove me crazy. I have a 7 thoiusand dollar problem just sitting in the garage,,cnt get my Harey started,

 

Definitely haven't got much sleep over the last week. I'm not satisfied unless every toy is up and running. Now back to enjoying it.

 

hey! I also have a 95 LT1 that sputters and runs rich, then the check engine light comes on and it runs fine. Was that the same that happened to you?