I'm having ignition problems with my '91 3.1L Camaro. Every few weeks my ignition control module (ICM) quits on me. Here's the puzzling part--the modules don't die. When the current one quits, I just swap in an old one. When that one quits, I swap the first one back in. (They also test good at Autozone).

I've been living with this problem for the past 6 months. I want to get it fixed because 1) it's embarassing, and 2) I'm afraid one day it'll quit altogether and leave me stranded.

Here's some data you guys may find useful:
1. The problem occurs with all brands of ICMs (Though the ACDelco one lasted twice as longs as the Wells/Sorensons).
2. Battery volatge is good:
12.6V with the engine off.
14.2V at idle.
When the problem occurs, jumpstarting does not help.
3. New plug wires, cap/rotor, and iginition coil (MSD GM Blaster).
4. The plugs are about a year old. So is the pickup coil. Pickup coil test good using the resistance test in Chiltons.
5. I don't think it's heat related. Last time it failed, it was after the car was sitting in 40° weather for a few hours.
6. No problem once the car is started.
7. No codes.
8. Pulling the connectors off the ICM and putting them back on doesn't help, so I don't think it's a loose connector.

If you guys have any ideas, it would be GREATLY appreciated.

 

You're overheating your ICMs. Are they heatsinked properly when you mount them in? Are you using LOTS of dielectric grease on the heatsinks when you mount them? If you're not, you should be!

When the ICM overheats, the car will not run, but once it cools down, it will start working again.

 

I tried using a lot of grease, and I tried using only a thin film. No difference (actually using only a thin film seems to work better).

I don't think it's heat related. The car can sit overnight in freezing weather and still won't start up. Likewise, I can drive for 4 hours staright, turn the car off to get gas, and it'll fire right up. Then when I get to my destination, and go to leave after a few hours, when the block is cold, it won't start.

 

If the problem is that intermittent, are you sure it's an ICM problem? I mean, if it will start sometimes and not start others...who's to say that swapping the ICM is what allowed it to fire... That's a tricky problem though...intermittents are the worst. All that comes to mind is faulty wiring somewhere maybe... I'm assuming that when it does, you try to crank it and you've checked and gotten zero spark...

 

i get a problem similar but i must ask you.. when the problem occures do you lose all power to the inside of you car. ie no radio and teh such.

my car is no longer reliant on the computers any hows

 

Saigon...your problem sounds like it may be a bad ground wire. Check em out!

 

yea i thought so too after finding the ground (neg batt to engine block was almost falling off) but i tightened it and the problem still occurs. i checked every ground teh i know of in the engine bay and all are tight

 

I have the same problem too. I went through all that u did. Lots of money and time. Even a new memcal. Still no go. Mine is a v-8.
I'm still puzzled. If you find out what it is let me know! I'm still testing everythiung too.

 

Nixon1--I have no idea whether the problem really is the ICMs. It's just weird that replacing them immediately solves the problem even though they're still good. I haven't done the spark test. I've been away at college with no access to tools (not even a socket wrench.) I'm home for Xmas, so "hopefully" the problem will occur again so I can do a spark test.

Saigon--no, I still have full power when the problem occurs.

Zstreet--can't say that I'm happy to hear that someone with the same problem hasn't figured it out as well.