I hope this info will help some of you who have been chasing those intermittant electrical problems. My 90 coupe with 155,000 miles started to show the following symptoms once it got hot:
-completely shut down while driving
-would crank but not restart until it cooled down
-with key in the on position the fans would cycle up and down, the AC compressor clutch would click, 2 relays under the dash on the drivers side would keep clicking as well as the relay behind the battery on the firewall and the air pump relays.
Checked every sensor and wire and ground and the last one that tested just OK was the coolant temp sensor so I decided to change it. The next hot sunny day I rolled the car out of the garage and swapped out the coolant sensor while the engine was cold. When I turned the key to the on position all those symptoms were back. So much for the engine getting hot I thought until I happened to lean onto the ECM which had been baking in the sun while I worked on the car. Went in the house, got some ice, put it on the ECM for 2 minutes and the symptoms disappeared. To make sure, I removed the ice, let the ECM bake again (had lunch) and the symptoms returned. This time I left the key on while the fans and AC clutch were clicking, put on the ice and after a minute, no more clicking. She started right up. New ECM and she revs like she just came off the showroom floor. Now I need bigger brakes!
Hope this helps and don't fake yourself out.

 

Good job.....glad to hear you got it!

 

Glad to see you found that tough problem. Have read and seen many stories on the 90-93 ECMs causing a wide variety of engine running problems and other strange happenings. Seems like your problem had many paths you could follow for troubleshooting. Definitely will keep this in the back of my mind for future reference with weird happenings.

 

I've always wondered if there was some way to protect the ECM from heat. Electronics and heat don't like each other. I've tried to increase airflow in the area to promote cooling.

 

Trying to keep the heat down is a valiant attempt. But fighting that heat from the engine compartment is an up hill battle.

Most likely the grade of semiconductors of some of the common devices in the ECM are not quite up to the task of the harsh environment. The reliability might have been better if they used a better commercial or military grade with better temperature characteristics. Possibly back in that time there was not any device that suited the operational parameters, but only Gordon the K might know.

 

The C4 really was an early experiment with auto electronics. A lot of our stock wiring is not sufficiently insulated for the heat under the hood. That is further compounded by our engines which tend to run on the hot side.

There were better insulators available then, but I don't think anyone thought it was necessary. After all prior to our cars, there just wasn't that many wires under the hood.

 

I’ve read an awful lot about these intermittent heat related problems with these ECMs and was wondering if anyone out there with a Heat related problem still has the old ECM and would be willing to crack one open and take a picture of the component side and a Hi-Resolution picture of the back side (trace) with all the solder joints. I’m convinced there are bad solder connections on high heat component connections (hi watt resistors, relay driver transistors, etc.) or hi frequency components (coils or transformers) I’ve not seen the inside of one of these but would like to try to save us all allot of intermittent Big Bucks.

Feel free to PM me.

Kevin..

 

Hi, some pic's of a -93 ECM, maybe not that hi-res to see all of it.
When my ECM failed, i checked every soldering joint with magnifying glass but could not see any bad joints. I think in my case a electronic component was bad.












Regards
MickeW

 

I am having a problem with my '92, all indications point to a failure
of the ECM. Can anyone suggest where I should send my unit to be rebuilt to working order. Car ran pefrectly one day, the next day no start,
Code 43, various tests all point to ECM failure.

Sure would appreciate suggestions of who does a good job, want my same original unit with chip--that is important as chip was made to work on this slightly modified engine.

 

Just exchange it at any O'reilly's or autozone. it comes with a lifetime warranty, and you can rest that it will never be a cost that you will have to pay again.
At least I hope they are still lifetime warranties...................

 

According to this post, code 43 is an EST problem for your year:

http://forums.corvetteforum.com/1576116036-post35.html

That means that the connection between the optispark and the ECM is open. Check your wiring and connectors related to the optispark. Some contact cleaner/spray might be helpful.

 

I noticed after buying my 91 Vette, that the original ECM was replaced.

I guess the previous owner had the ecm failure but, it's been fine for the past 7 years I've owned the Vette!...

 

By '91, GM was beginning to sort out ECM failures, and prior to that they were particularly fickle (my '89 had 3 replaced under warranty). They still failed though and a lot of the Service Manuals through the late '90's instructed techs to hook up something to the heater outlet that the Tech would then aim at the ECM to heat it up. If the heat duplicated whatever the problem was, you replaced the ECM. ECM warranties became progressively longer - much longer than the basic (you can thank the EPA) - and that seemed to improve the manufacturing process. Gross failures today would probably provoke a massive recall.

 

I just noticed how old this thread is. I also have been having intermittant problems with my black 92 when left outside in the hot south florida sun. Mine will start up like normal then begin to run rough and start to backfire through the exhaust really bad for about 30 seconds . The engine will smooth out and back to normal Without any codes other than code 12. Was never left stranded and nobody could figure it out because it only acted up for 30 seconds or so on start up. Lately been hoping it would just die so we could find the problem. I never did what Achille did with the ice routine great idea. My computer is also a rebuilt delphi. Great to hear when someone fixes their intermittant problems it also gives me hope. I have replaced all the typical things that could cause this just never understood why it only does it on start up engine hot or cold when left in the hot sun !!!