I too took my '93 out Saturday as it was so nice out here in Michigan. I was 30 miles from home and was watching the digital temp go upto 235 and than the engine died. I let it cool for about 20 minutes and it started as I decided to head home. Got about 3 miles did same thing. Did this 4 times. Than I noticed that the fans were not running after I stopped. I assummed that even with the car off one or both fans should be running yet. I than got to thinking that if I could jump the wires on the computer I knew the fans would come on. Found a sohort piece of wire and sure enough the fans came on and brought temp down in just a few minutes while the engine was off. By doing so it was posting codes but only 12 was coming up, no others to show that there was a problem with anything. Went about 8 miles and the wire fell out and engine died. replugged the wire in and got closer to home and died 2 more times in the next 16-20 miles. I am assuming the relays for both fans are ok since they came on through the computer hookup??? Also read that several other items the ECM reads before turning fans on at around 220and 226 respectively for each. Coolant Temp sensor, Oil temp sensor, air sensor I think refering to the one in the throttle body which mine has the extension on to move it further towards the air cleaner and or the ambient air temp sensor up by the bumper which I know is not registering right, and a sensor in the A/C monitoring pressure in the line. The A/Cwas working when I picked up the car last year, and when I tried it on Easter it was not cooling so sensor may not be working there if low on freon. I had drove the car over the last 2 weeks 4 or 5 times and seemed to be ok except for the analog gauges did not correspond with digital for oil an coolant temps.

As many thread's I am making about the car, you may think it is junk with all the problems I am having. Certainly not going to give up! I think using this type of vehicle too little does more harm. I feel to enjoy it it has to be driven.

Really appreciate everyone's help. Thank's.

 

Codes in computer?

http://www.corvettebuyers.com/c4vettes/codes.htm

Some things have to be right before ALL others - fuel pressure included. Check it. Static (motor off), motor on with vacuum off of fuel pressure regulator, and motor on with vacuum ON FPR.

Check static last, and leave the gauge on the line. Watch it, and see how long before pressure drops to zero. This will tell if injectors are working ok, or if they are 'leaking'.

 

ICM could be the culprit. Also, the fans do not run once the car is shut off. The only thing that turns the fans on is the coolant temperature via the ECM if I remember correctly. The ICM could be getting hot and shutting down the car. When you let it cool and then it started sounds like a classic ICM failure in progress. I have a feeling the wire has nothing to do with the car starting - it shouldn't. Just by jumpering the ALDL into diagnosis mode would not have anything to do with it and I wouldn't drive the car like that anymore. I bet dollars to donuts its the ICM or the coil. The only way I can think of that the wire might have helped was that it somehow put the car into "limp" mode and if thats the case then its not the ICM but thats doubtful.

 

I had just put the new coil and module on replacing the Delteq system. I also put a washer behind the bracket than the heat sink and than the module with the dielectric grease that comes with it. If that indeed is it should I space it out more behind the bracket and engine, perhaps a nylon washer so it won't transmit as much heat. Maybe more grease on the back of module and not tighten it as snug, letting it have more cushion to it.

 

You have to remember that dielectric grease is not a heat inhibitor. Matter of fact, it will transfer that heat directly. Granted, you used the heat sink so that should have taken care of that. I think what you have done should have been sufficient. I would check the coil and module even though they are new. If the heat got them then at least you would know where to start.

 

I actually did that on mine - dielectric grease, instead of heat sink paste. And I even had some in in my computer parts box for the graphics card fan. Worse yet, I haven't wiped it either!!!

Scott - what codes do you have?

You can get the ICM tested at Advance / Zone. Un-seize the screws that hold it in to the head bracket, drive there, and get it tested HOT. WATCH the test too - some of them don't know how to test it...

 

I had a code 42 when the Delteq system was on. It went away when I put the new coil and module on. I also noticed Saturday that the A/C clutch was not coming when I had the air onthe week before. I checked the relay by putting a new one on. I tried swapping the relay next to it for the transmission but it did'nt turn on either. Napa only had one in stock. Jumping two connectors engaged the clutch and turned primary fan so I know compressor is working and fan relay as I thought i had a heating problem. Got to look at the wiring diagram a little more to see if I am getting a signal to turn the relay on.

Can the Tech 1 check the coil and module as my neighbor has that available from GM dealership he works at.

 

We seem to have more than one problem here... I suggest clearing ALL codes - PCM, CCM, DERM, and ABS codes -
http://www.corvette-guru.com/modules...d=5237&forum=1
I would have posted more info there on that, but they were worried about copyrights issues.

After clearing, pull the trigger, and let it run until warmed up, everything OFF. Let's get some basic reads on the machine here...