Icm getting too hot?

[Danpatters583]

Hello all,

 

I have '90 Retta and I have a strange issue with it. I've swapped out the icm with the Delco icm. I did it like 3 years ago. Shortly after, I've always had this weird missfire issue. And it only seems to be an issue after the car is very hot. Worse during the summer. And has progressively gotten worse. I Will add that, it seems to only be an issue in stop and go heavy traffic. On the highway it seems to get plenty of air and everything works.

 

Kinda running out of things to check. All sensors seem to be running and working with in spec according to the on board diagnostic system.

 

1) I've checked grounds and cleaned them

 

2) swapped out icm with known good ones (3 different  ones) same issue happens.

 

3) I've cleaned off all the old heat sink paste and applied a new thin coating. Like I've done on other ICM like my old Nova or like a PC's CPU.

 

4) tested my modules in my dad's old lesabre with the same system. Mine run his car for hours. No issues.

 

The only thing I can think of at this point is that, the module gets WAY too hot and shuts off afterwards. Again, only in stop and go/ heavy traffic. If I let the car sit a while and cool, it seems to run like nothing happened. Runs fine. Which I why I believe I have something getting too hot. And seeing as the ICM for these cars seem to get hot normally, maybe mine are getting too hot? 

 

Anyone else ever run into this issue? If so have any ideas or recommendations? Short of building some sort of heat sink set up, im out of ideas. 

 

 

[Ronnie]

Wipe off all the heat sink paste and bolt the ICM to mounting plate metal to metal. I see no reason to use paste if both aluminum mounting surfaces are clean. Aluminum is an excellent conductor of heat without any paste.

 

I'm no electronics expert but when I look at the wiring diagram for the ICM (below) I see it having a chassis ground. The heat sink paste might be insulating the ICM from the mounting plate that grounds it. I might be wrong about that but I would remove the paste and see what happens.

 

[Danpatters583]

Interesting.  I will give that a go and see if that changes anything! Thank you for the diagram. I am gonna double check that ground for resistance levels to ensure it's good as well. I will let you know what happens! Hopefully I'll get a chance later today to check that.

Edited May 20, 2023 by Danpatters583

[Danpatters583]

So I tried what you recommended. Seemed to make a difference at first.  Drove around with no issues and sat for a while, while I was at the gym..  Went to go leave the gym and it started acting up again.  So, I swapped icm with a spare one. Got about 10 minutes down the road and same thing.  Then I thought what if I got a bad coil? So I swapped out the msd coils (given to me for free and I liked the look of them on there lol) with stock ones I have as spares. I drove it around for about an hour with no issues and better than ever idle. So Im thinking I had a coil or two that was sensitive to heat? Does that make sense? I've had a few 3.8 and I've never seen one of their coils get heat soaked and have issues.  I've seen them flat out fail. But never be Intermittent like that. I Drove it to work this morning and no issues. I'll see what happens when I drive home. Supposed to be pretty warm out. 

[Ronnie]

36 minutes ago, Danpatters583 said:

So I swapped out the msd coils (given to me for free

Sounds like you have found the reason they were free. 🙂 

[Danpatters583]

I suppose so! I just never heard of a coil being intermittent like that. So strange.