How hard is it to change the ICM on a 93 LT1?
06-13-2018, 11:39 AM
#1
Heel & Toe
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How hard is it to change the ICM on a 93 LT1?
I have a 93 C4....it currently has this issue where it starts fine on a cold start, but if the engine gets hot, it fails to start. The local mechanic believes it to be the Ignition Control Module. Although he says it's a real pain in the *** to replace as it's located inside the distributor, and apparently it would cost over $1,000 to replace the part(s) in question.
Is this really where the ICM is? I see ICMs listed online for fairly cheap ($60-$70), so most of the cost to replace would be the labor itself I'd imagine.
So, is it really that much of a pain in the *** to replace?
Is this really where the ICM is? I see ICMs listed online for fairly cheap ($60-$70), so most of the cost to replace would be the labor itself I'd imagine.
So, is it really that much of a pain in the *** to replace?
06-13-2018, 02:53 PM
#4
Burning Brakes
It's on a bracket with the coil. There are two bolts holding it on, and I think 3 wire connections. If it hasn't been replaced before you might need to drill out two rivets, but that might be the coil. After that it's just remove the old, and add the new. When installing the new ICM make sure to use thermal compound on the ICM. You should be able to change it.
PS
Don't use dielectric grease. You want thermal paste, heatsink compound, or similar. It will cost more, but you can buy thermal paste from many places that sell computer parts.
PS
Don't use dielectric grease. You want thermal paste, heatsink compound, or similar. It will cost more, but you can buy thermal paste from many places that sell computer parts.
Last edited by aDigitalPhantom; 06-13-2018 at 03:24 PM.
06-14-2018, 07:11 AM
#7
Le Mans Master
All the above is correct. Your mechanic is right to suspect the ICM, but wrong in where it's located. I guess he's confusing it with the optical sensor inside the Optispark distributor? That sensor can fail with heat soak, too, but more often it's the ICM. Before throwing parts at this problem, I'd do some diagnostics to narrow it down. There is a good guide here: http://easyautodiagnostics.com/gm/4....test-the-icm-1. You'll have to do this testing while the car is failing to start, of course. You can also call your local parts stores to see if any of them still have the equipment to test an ICM - it used to be that they all did, but not so much anymore. If you find one, have them run the test a couple times to let the ICM get really hot. It may not show bad the first time they run the test on the cold ICM, but the test will get it hot pretty fast.
06-15-2018, 02:42 PM
#11
Le Mans Master
It just takes a thin layer to squish between the bracket and the metal backing plate of the ICM. The idea is to have continuous material contact from the ICM to the heat sink in order to all the ICM's heat to transfer to the sink as efficiently as possible.