1990 3.1L ignition control module

[45es]

I am also having ignition control module failures. I installed the 1990 RWD 3.1L in a older Jeep and control it with a 1227727 ecm. Within the last two weeks and less than 50 miles two ICM have failed while driving. When the first module failed I checked for codes (none), checked the wiring and connectors for any problems and did not find anything. After I installed the first new ICM two weeks ago everthing seemed fine until today when the second unit failed. Anyone have a suggestion as to where I should be looking for the cause of these failures? Could the coil, alternator or even the ECM possibly lead to a failure?

Ed

[Purple pit]

I read somewhere to put computer heatsink grease on the back of the ICM where it meets the mounting plate. They said it acts like a heatsink and moisture can get betwwen the ICM and the mounting plate and cause uneven cooling(cool spots next to hot spots). You just need a thin coat of the heatsink grease, don't go wild.

[geoffinbc]

Agreed you should clean and replace the grease every time. Also if you are not using an AC Delco (will have a GM stamp on it) then you wont get any descent life out of it. Also the coil plays a big role in the life of the module. If the primary windings have too low of resistance then it can cause the module to overheat. I would replace the module and coil as a pair with AC Delco parts and it should last as long as the very first set did.

[Purple pit]

That is just what I did on my 90GT 3.1L. I lost two coils in a months time. When looking around online I found a post on some GM FWD site about the heatsink grease. I bought a BWD ICM (they were good at the time, now they have three levels and only the top end is worth anything) and some MSD coils( the last of the US made ones). As a person that is a bit nuts I cleaned both sides of the mounting plate with laquer thinner. On the front side rubbing alcohol was used after that and the grease was spread with a credit card on the back of the ICM(after it was cleaned with rubbing alcohol). Then the ICM was bolted to the plate. The nuts: I did the same to the front(that is not needed). Dielectric grease was used on all connections. I never had a problem after that.

[45es]

Thanksfor the replies. I know about the importance of the dielectric grease and was sure to use it when I replaced the ICM. With a little more research and talking to a mechanic freind, the general recommendation was to replace the coil along with the ICM. I followeed the recommendations and now have a new coil and ICM. The Jeep is back up and running but there is a sporadic miss which does not make sense to me because everything else in the ignition system system is new (pickup coil, distributor cap, plugs and wires.

[Purple pit]

Oops I was talking about the ICM for the FWD 3.1's. Did you replace the rotor?

[45es]

Yup.

[geoffinbc]

I would suggest pulling all the plugs and carefully inspecting the ceramic insulator and also look at the ends they should be clean or slightly golden brown. It is easy to crack some of the insulators on the iron head motors because of the angle you have to work on to get the plug socket on there. Plugs and Plug wires are your number one cause for misfire.

[IDCavalier]

Bob over at DynamicEFI.com (supplier of my ECM) knows my situation and suggested that a bad alternator/ one that is going on the fritz can cause voltage spikes that will fry an ICM.

I bought the most expensive BWD ICM with BWD Select coils and BWD CKP to match earlier this year when I wanted to be done with this mess once and for all.

Also, I neglected to mention that this is a DIS setup. 3 coil packs mount to the ICM and hold it to the plate.

LOCATION: Sandwiched between the HOT cast iron exhaust manifold and the starter. (Gotta LOVE FWD!)

[Purple pit]

Bob over at DynamicEFI.com (supplier of my ECM) knows my situation and suggested that a bad alternator/ one that is going on the fritz can cause voltage spikes that will fry an ICM.

I bought the most expensive BWD ICM with BWD Select coils and BWD CKP to match earlier this year when I wanted to be done with this mess once and for all.

Also, I neglected to mention that this is a DIS setup. 3 coil packs mount to the ICM and hold it to the plate.

LOCATION: Sandwiched between the HOT cast iron exhaust manifold and the starter. (Gotta LOVE FWD!)

I got your PM, but when I look at it the site locks up and I have to close IE. By the way for 12 years I had a 90GT Beretta with a 3.1L. I sure know what it's like working on the coils/ICM. I just had to push the radiator out of the way a bit by taking off the upper mounts. Lucky me.

2nd on the wires. A cheap set will kill coils in no time. GM plugs should be used, others can cause problems.

[IDCavalier]

OK Thanks everyone!

I will post results as soon as I get the Camaro out of the garage...

Yup! I bought a Camaro! 1994 3.4 with a T5.

BUT I want to post results on the Cavalier ASAP.

Thanks again!