Just recently bought my first corvette, it's a 1993 base lt1 with 133k miles on the clock. On its drive home and the few days I've gotten it out in the week sense I've got it the car hasn't skipped a beat. I was gathering some tune up items and decided to check the coolant to see if that needed a change sense it would get up to 238 degrees and continue to climb without kicking on the fans. Sure enough the coolant was a dark brown and tons of road gunk hand built up on the face of the radiator.

Bought a new 180 degree thermostat, new hoses, fan relays, temp sensors, knock sensors and coolant. Spent a good part of a day replacing it all and doing a coolant flush, all was going well until I took the car off the jack stands and filled it with coolant. Before doing the coolant flush it would get up to 220 degrees just fine and would get down to around 200 while I was moving. Once doing the coolant flush though I can start it up and it will run just fine until it hit 180 degrees and it would die. I would immediately try and start it again and it would just crank with no start and eventually back fire through the intake. Let the engine cool off and turn the key and it fires right up and runs great until that 180 degrees and it dies again. It threw a dct 43 code which following the service manual it led me to a faulty ICM, replaced the ICM and it runs better than I've ever heard it run, had hopes this would fix the issue I was having but nope. It got to 192 degrees and die, immediately turned the key again and it actually fired back up this time and it proceeded to get 220 degrees. Once it reached that 220 mark the rpm began to struggle, it's idle fluctuated and wanted to die and once at 223 degrees if you touch the gas pedal it immediately bogs and starts misfiring. Any solution to this would be greatly appreciated

 

I'm just shooting in the dark here, I don't have any direct experience with this. I'm just going by what I've read and putting 2 and 2 together.

Did you by chance let any coolant run down toward the OptiSpark? It's below the water pump and if water gets in it, it really screws it up. I think the symptoms you're experiencing are similar to those that others with bad Opti's have reported.

Again, I'm just going by what I've read, so take this for what's worth - which may not be much!

 

I hope you didn't get the Optispark wet, the could create major headache, has you just learned.

 

So if I understand ..... the engine ran quite well prior to the replacement of maintenance items?
Are you aware that the Gen-2 LT1 uses a different thermostat that the older 350 designs (because of the reverse flow design)
Also the temp sensor at the front of the engine by the thermostat housing is the sensor that sends it's signal to the engines control module used to determine when the engine is in closed loop. Sometimes this important sensor gets damaged when replacing things.

Each year functions slightly differently .... but on my 95 both fans come on at low speed when the "digital" temp display (this is that signal from the temp sensor at the front of the engine) reaches approx 228F (they turn off after an approx 5 degree drop in tenp). the fans do not come on at high speed until the digital temp reaches approx 237F and after a 5 degree drop they switch to low speed.

 

to my knowledge I didn't get any water on or into the optispark. Was very carful flushing the coolant and replacing the temp sensors knowing the issue it could cause for the optispark because of my 97 z28. I very much appreciate the feedback, even though I didn't get anything onto the optispark I believe it still has the original in it. This unit looks extremely old but at the same time it's completely possible that I bought a damaged sensor or damaged the new one while installing it.

 

Yea it ran very well, alot better than I had expected. The only thing I noticed that wasn't good was the color of the coolant and the fact that when it got to around 230+ degrees the fans wouldn't kick on and it would rapidly climb to 260. I've now got the fans working and it's actually very difficult to get the car to run over 220 degrees now but I believe something electrical isn't liking the heat because once at that temp it just doesn't want to stay running.