corvettezo7sp

To start, that's say that I have been replacing ICM's on this car for the past 2 years and since replacing the factory original the later ones have been dying faster and faster until I was replacing one every month. After the next one started dying after only 2 weeks I finally decided to move the ICM off the block and attached a big computer heatsink to it. Success! I have been going 4 months without any problem whatsoever ignition related. What did not make sense to me though was why the heat was killing the ICM module when it was designed to work that way.

So, I dug a little deeper. About 2 years ago the car developed a ticking sound (about 30k miles ago) and it seems to go away or come back at random times. Made no sense. My spark plugs were all on tight, and the ticking sound almost sounds internal. One night I was under the car trying to find this ticking sound. Hood was closed and it was really dark out. I noticed a faint blue glow all the way around the engine. These plug wires, although, not old at all, were leaking through on the ground points of the engine. Leaking through their own insulation onto themselves. So my guess is the ticking sound is probably coming from a cylinder that is firing before it is supposed to. Let me stress faint by the way, because I still cannot see it if i am looking directly at it. Only out of the corner of my eye could i see it. Needless to say I am replacing my plug wires this weekend and will be mounting the ICM back onto the engine. I will post back if this cures the ICM problems, as I do believe the ICM's were literally being zapped. Also, if the ticking sound goes away I will let you all know as well.

-Ryan

Winnin'

what are all your. Symptoms of a bad ICM?

1963SS

I always mount my ICM on a small piece of aluminum, use plenty of thermal joint compound and space it off the block about three washers worth.......maybe 3/16". Most electronics really like to be kept below 140 degrees and it can't hurt a thing. Most commercially rated IC's are rated for -40 to +85 Celsius or about 180 F. Vettes run hot and while failure is rare it does happen.

corvettezo7sp

They were quite odd but always cleared up when I replaced the ICM. The major issue I had was when the engine was warmed up I would come up to a stoplight and the engine would just run rough. It wouldn't smooth out until it ran above 2400 rpm again. Another issue was during the morning start it would run like it was firing every other cylinder or fire the engine backwards a couple times. Also when I did get going it had a slight hesitation and power would jump around as if the computer was retarding the timing. The worse one was a no start no spark when it finally died. I'd replace it and it would be fine for a few weeks. I honestly thought my optispark was going bad.

corvettezo7sp

True. I forgot to state this was for LT1 vehicles only. Is the title editable? The LT1 ICM should be rated at -40 and +125 degrees Celsius. Although that always sounded a bit high for me. Would you mind posting a picture of how your is mounted? Thanks. Even if there was a heat problem I do not believe I should have replaced the ICM 8 times in one year.

-Ryan

Winnin'

I'm kinda seeing the same thing. Did yours run perfect when cold, then once warmed to around 180* start acting up? Mine runs like new till warmed up, then has a rough idle and if you blip the throttle you can feel a low RPM miss. While driving it'll be okay when not under load, but if you floor it, it'll miss like it running on 6 cylinders, pop, and can even here valve rattle. All this, but when cold, it'll put you into the back of the seat like it was new. No check engine light either.