1993 3.1 MPFI Ignition Module

[IDCavalier]

Hello Folks!

Just wondering...

I have a 1993 Chevy Cavalier Z24 and I keep going through ICMs like they're going out of style!

Has anyone heard of this before and what do I do?

I've gone through three of them this year and my neighbor is getting tired of towing me home!

The problem seems to be getting worse as when the original ICM went out, the wells brand replacement lasted about a year, then a BWD lasted almost a year, and now I can't get more than a month out of a brand-new ICM.

Any thoughts?

THANKS!

[caffeine]

I have no idea if something could be causing the ICM to go bad, but I've never used anything but OEM ones. Considering a whole coil pack can be had for $20-40 it's hard to go wrong.

[Purple pit]

Try some CPU heatsink grease on the back where it contacts the mounting plate. Just use a thin coat(spread it with a credit card or something like that). Make sure both surfaces are clean before you do it.

[IDCavalier]

Thanks guys, for the input!
But I have done the above prescribed procedure for all of my ICM installs.
I am really meticulous about my work on this car. I even planed the mounting plate with 220 grit sandpaper this last install. Following, of course, with the traditional acetone and alcohol wipedown before carefully smearing HEAT SINK grease (not included BTW) between contact surfaces of the ICM and mounting plate.

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!)

Doing ANY work on the ICM/Coil Pack assmy requires removing the starter! I've already worn out the hole on one starter, just working on ignition!

SO I'm at a loss... PLEASE... any suggestions are welcome as I have tried a LOT of the more common remedies to no avail!

Thanks!

[88GTRacer]

I world relocate the ICM closer to the firewall. IIRC, all you need to do is pull the wires from the loom and extend a ground cable.

Sent from my BlackBerry Z10

[IDCavalier]

I REALLY wanted to. I tried one time, thinking that I could just put it on the firewall. I should have test fitted the bracket before pulling all the wires out of the loom! Because there is no room for it there.

Maybe I could build a bracket for it somehow, but they have REALLY shoe-horned this thing in there!

I want to relocate it, but I also think that I have another issue... something electrical, maybe. I only say that because the original ICM lasted for 15 years (I'm guessing) and 160k miles.

[IDCavalier]

Has anyone ever heard of an electrical issue that causes ICM circuitry to go bad?

I can't help but think that it is something that I have done, like installing the aftermarket ECU, that is causing these ICMs to go out so quickly...

[Superdave]

Make sure the ground wire is good on the 2 pin power plug, I can't remember exactly where it runs in a Jbody anymore though. It could ground to the post above the starter or around on the back side of the bellhousing.

Either way, check the resistance between the ground wire and the engine block.


Also, test all three coils. One could be bad and hurting the ICM. They are easy to test with a multimeter and a paperclip.

Check the resistance across the primaries (Input side from the ICM) and then the secondaries (posts). All 3 coils should be close to the same.

[IDCavalier]

Make sure the ground wire is good on the 2 pin power plug, I can't remember exactly where it runs in a Jbody anymore though. It could ground to the post above the starter or around on the back side of the bellhousing.

Either way, check the resistance between the ground wire and the engine block.


Also, test all three coils. One could be bad and hurting the ICM. They are easy to test with a multimeter and a paperclip.

Check the resistance across the primaries (Input side from the ICM) and then the secondaries (posts). All 3 coils should be close to the same.

Awesome! Thanks Superdave!
I've been waiting to get some diagnostic tips.
I just wasn't sure where to start!
Thanks again, I will post results!
AFTER I get the trans back in my recently acquired '94 Camaro 3.4L!

[Guest]

I never pulled my starter to re&re my ICM/coils in my FWD genII 660 stuff. Yes it was tight, but it's completely do-able.

In addition to the ground wire to the coil pack, check the ground strap between the engine block and chassis, and between the battery and ground. While you're at it, checking the main ground cable between the battery and the block wouldn't hurt either.

As you have been told an alternator with a noisy output or failing rectifier diode can cause issues with electrical components as well, have this checked. You can't check this with a DMM, at least not any common DMM, only one that has the functionality of an Oscilloscope (Plotting very small voltage changes over time) will be able to detect this, and only if you know what to look for.

Also stop using heat sink compound. These were always installed dry and the only time I've heard of multiple failures of ICMs that wasn't a noisy power problem was when people used heat sink compound. I've never used heat sink compound or grease when I've installed any ICM, and have only ever had one ICM fail in over 20 years of driving or using GM ICM equipped vehicles and that was due to water while washing my engine down.

[IDCavalier]

AWESOME!

Thanks!

I just KNOW that I'm doing something wrong. I will check EVERY ground forward of the firewall.

It sounds like it may be cheaper to replace the alternator too, if the ground check doesn't do the trick.

I have a pretty big sound system in the car, but I have had that for years before I started having so many ICM problems. But if I AM having alt. problems, that might have strained it over the years...

BTW- what's a 660?

[bszopi]

BTW- what's a 660?

Its just a shorter abbreviation for a 60 degree V6.

Brad
via Moto X

[IDCavalier]

Oh, OK.

Thanks! I will use that more often to sound more experienced.

'Cause I HAVE turned a few wrenches, I just don't always get the jargon.

Thanks again!

[IDCavalier]

OK-
Sorry for the delay. Just bought a '94 Camaro and was stoked to get it on the road!

Back to the ICM... I pulled it and ohm checked the ground wire to the block and it is as low as touching the leads together.

BUT, the harness itself looks like it's a little loosey goosey. I'm talking about the actual female pins inside of the connector, esp. the ign power and ground.

Think THAT might be where my trouble lies?

Also, I took the ICM to O'Reilly's to have it tested, and it passed two iterations, and it was HOT after the second.

That's weird because I feel pretty sure that it failed on me. I had to get towed across town!

EVERY ground forward of the firewall is nasty and corroded! SuperDave is on the right track!

I'll clean and tin all the grounds, solder new harnesses and reinstall.

Will post results...

[45es]

Did you ever get the car repaired? If so what did you ultimately find was the cause of the ICM failure?