Replacing the ICM

[Jon Boy]

Hi, all. I've got some problems with my '93 Cutlass Supreme 3.1 and am looking for a little help. It'd been idling rough for quite a while, and the other day it wouldn't start when it was hotâ€â€just cranked and cranked but started fine once it'd cooled down. Then it died on the freeway as if I'd just switched off the ignition and wouldn't restart until it was cool again.

 

I did a little research and figured it was probably the ICM overheating and killing the spark. I drove it to a dealership to have them take a look at it, and it died again on the way there. A little water sprayed over the ICM, and it started up fine. Their diagnosis confirmed my suspicionâ€â€a bad ICM and crankshaft position sensor. They quoted me $700 for parts and labor, which just about made my eyes pop out of my head.

 

So my question is this: how hard is it to change the ICM myself? Since the ICM is on the front of the engine down by the header, how big of a pain is it going to be to get to? Also, the Chilton manual says that I need a Tech 1 scan tool to relearn the idle after I replace the part but before I start it. Is this really necessary? I searched and couldn't find any mention of it on the forum, but maybe I've missed something.

 

Thanks for the help.

[mfewtrail]

You do not need a Tech I for an idle relearn. Some cars do not even need to relearn the idle. My '93 Grand Prix usually needs to relearn it's idle or it will stall when coming to a stop after driving down the highway. After hooking the battery back up on it and finishing a repair, I start the car with my foot on the brake and immediately put it in drive. Then I let it idle for about 5mins and the idle is relearned. Talk to 10 people here, and you'll probably hear 9 different ways to do an idle relearn..there's no real set rule for it, but my method has always worked for me.

 

As for the actual repair, the manual you have pretty much has it covered. Make sure to disconnect the negative battery terminal before working on the car. Remove the three 13mm bolts holding the ICM on and THEN remove the coilpacks from it after you get it out of the car. As for the crankshaft position sensor, rotate the engine forward and you'll see where it resides on the block(it's pretty much inline with the alternator). When you remove the 10mm bolt securing it to the block, take and twist the sensor a bit in it's bore to get it moving before trying to pull it out. They have a habit of breaking off in the block when they're older and get brittle. Twisting the sensor before or while pulling it out helps free it up. For what it's worth, Advance Auto and a few other part chains have ignition modules for about $90. CPS's are only about $20. An original AC Delco ignition module will be about $180 new, most parts stores can get these too. Maybe someone here will chime in that's used the $90 version...I would imagine they work fine, but probably will not last as long as the AC Delco ones. The original ICM on my '93 lasted 254,000 miles. I went with an AC Delco one when I swapped mine out as I had a known good low mileage spare from another 3.1 engine.

[slick]

Be warned, some of the bolts to get the ICM off can be damn near impossible with the tight space, but it is possible. 6 bolts total hold the coils in place, and a few more bolt the ICM to the engine itself.

[Jon Boy]

Thanks for the advice, guys. That helps a lot.

[ns87]

If you do it from the top of the engine remove the radiator fans and stuff. If coming from the bottom, get a lot of extentions. Its frustrating bc of tight space, but it isnt the worst repair in the world. Keep us posted