What are the symptoms of a faulty ignition module. The car acts up, cuts out, and sometimes dies only after I drive for several minutes (starts and runs great when cold). I had to relocate the module and finned aluminum 'mount' to the PS reservoir a couple years ago when I installed a full size coil (and MSD 6A). It IS grounded, but I noticed today after it died that I was NOT getting any spark at the plug wires and that finned aluminum 'mount' was almost TOO HOT to touch. I recently replaced the Opti (had a screw loose inside it) and changed back to my Autolite plugs and it ran great for about 1 day before acting up. EVERYTHING is new or a couple years old (ALL less than 10,000 miles) EXCEPT for the ignition module, which is probably the original '92 (around 100,000 miles).
I scanned it- NO TROUBLE CODES FOUND.
I bypassed the MSD and Hi-Perf coil, back to stock-Still acts up and dies when good and warm.
I have a fuel pressure guage on the windshield- No drop in pressure when it cuts out. (When it cuts out and comes back, it comes back hard and strong, so I don't think it is fuel related)
Seems most noticeable close to 4,000 RPM, whether I rev it slowly or quickly.
Car will start with no probems the next day.
Car has a new battery and slightly larger ATI damper/pulley, so it idles around a strong 14.1 volts according to scanner.
According to scanner, timing is normal-not jumping around.
The car friggin' screams and will rev beyond 4,000 easily when not 'acting up'.

 

Take your ignition module to Autozone and have them run it through 10
cycles, gets pretty hot by then and you really can't tell if it's good or bad until its cycled to the point it's hot.

 

Although the symptoms sound like a bad ignition module and it should not be getting that hot. Did you check to see if it still had the white grease between the ICM and the cooling fins? This is VERY important so that it can dissipate the heat generated by the ICM. However when the ICM is going bad it will usually just burn out and not work any more.

I had a similar problem on my 92 and after changing the ICM it came back in a few days whenever the engine was hot. The problem with mine was the connection to the ICM. The weather seal in the plug was missing and over time the vibrations had opened up the female side of the connector pins slightly and when they expanded from the heat they would lose contact intermittantly. Usually after cooling it would start and run again.

Try testing the connector by wiggleing it about while the engine is started to see if you can duplicate the problem. Take something pointy and close the female contacts some to give a better contact and make sure the rubber weather gasket is still on.

 

Thanks guys! Through the years I have unplugged and plugged the module from the harness connector countless times. If I remember correctly, there is no longer any grease behind the module itself. I do not have an Autozone, but I may call around for a cycling test.
I can get a new Borg Warner replacement for $95. Are there any better alternatives or 'hi-performance' versions available (and where?)?
Thanks again, Joel.

 

couldn't get thread to advance??

 

No grease will cause the ICM to burn out prematurely. $95.00 is way too much for a ICM, mine cost $29.00. No need to go high performance on this the GM one is the best to replace it with. I replaced mine with an Echlin as routine maint and it burnt out in 2 weeks, put back the oroginal GM one and it still is running fine.

 

Will the part number on my old module get me one from my GM dealer? If it is not a Buick or a 4WD truck, its a gamble to get the right part from them on the first try.
It probably won't come with any grease. Do I just use some dielectric silicone, or is it something specific?
Thanks again, Joel.

 

Use a dielectric grease available from any good auto store. I just bought a tube from NAPA for $4. I used this in the distributor housing just under the coil assembly. I used the same grease between the module and the distributor housing. No grease between the module and housing will cause the module to overheat as stated above.

 

The white grease comes with the part. Dielectric grease will work but will melt off due to the high underhood heat so you will have to reapply periodically. The white stuff stays on forever.

 

Make sure you apply a thin coat of white thermal conductive grease to the back of the module.

Thermal grease is used to thermally couple the IM to the mounting base, the plenum in this case.

Thermal grease is a terribly bad thermal conductor but it is better than air. There are different types.

Probably the best ones have micro-particles of silver suspended in the grease. No matter for this application if the grease is somewhat electrically conductive, it's outside the IM anyway.

You probably need to apply the grease only once, if you replace the IM.

When the IM fails you will know right away because the car doesn't move anymore. When they fail, they fail.

My only experience to the exception was my neighbor's Chevy Astro van after 10 years of life. It had to be pulled to the garage until he figured it out.

 

I am fighting a very similar runability problem with my 94 now. Just ordered an ICM from GMPARTSDIRECT for $75, best price I could find for GM replacement. Intermittently cutout/misses at idle or higher RPM, or under high load, worse after gets hot. Had changed optispark and was good for 2 months, then same problem again. Just changed opti again with no improvement. Everything under hood tests good so I'm going for the ICM now. Coil was first thing I changed last year. If this don't fix it I'll be chasing wires and connections next.

 

I finally tracked my problem to the MSD cap and rotor kit on my Optispark, but I was also seriously questioning my computer/ECM. This was after ruling out the coil, plug wires, etc.