C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Icm ?

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Old Sep 13, 2010 | 11:49 PM
  #1  
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Default Icm ?

After getting through my weekend troubles with my car in an earlier thread, my car is running clean again. Now a new problem has emerged. I replaced the coil last week with an MSD. Is it possible this coil is smoking the ICM as I have read this somewhere else before but I am not sure ? As soon as the car got warmed up it would buck, miss and stumble under throttle, idles fine but as soon as I gas it it goes crazy and my tach goes nuts too. Confused I went home, it sat for 30 minutes and I fired it up and it revved fine again until it got hot.
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Old Sep 14, 2010 | 12:17 AM
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First of all get rid of the MSD coil. The Coil that comes with the car is plenty enough of a high energy system for the car. I do not trust the msd and have heard they can cause problems with the Opti. After replacing my opti twice that sucker came off and its for sale lol
Second get some washers 8 of them to be exact and move the ICM and coil off the head. Night and day difference with regard to temperatures and longevity of the ICM. You may need a new ICM not sure at this point but it sucks up way to much heat off that head and it is definitely a poor design with respect to being bolted to the head
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Old Sep 14, 2010 | 12:33 AM
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I have the old one, I will put that back on as it was not bad. I was wondering if that coil was at fault for all the erratic behavior.
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Old Sep 14, 2010 | 12:42 AM
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The coil could be a problem yes but so can the ICM which sounds to me like it could be getting heat soaked. Also have you gotton any codes
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Old Sep 14, 2010 | 01:22 AM
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No codes
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Old Sep 14, 2010 | 09:29 AM
  #6  
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I too put some washers between the head the bracket and the heat sink using some nylon ones so as not to transfer so heat, so that just left the bolts which I bought slightly longer to offset the washers, and it seemed to help as I had similiar problems. I used a napa coil and icm.
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Old Sep 14, 2010 | 05:07 PM
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Some interesting points. I fried my OEM ICM when I installed a MSD blaster. I had the old GM unit to put back on the car. Maybe I should chunk the MSD coil, and save a ICM. I understand the heat problem, but wouldn't nylon nuts isolate the unit from it's ground connection? Should a seperate ground connection be ran?
Thanks!
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Old Sep 16, 2010 | 12:31 PM
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I think I put the washers between the bracket and head. The bolt is metal to the bracket plus it is threaded into the head. I would have to take a look at it for sure.
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Old Sep 16, 2010 | 03:35 PM
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No help with the coil here but I had problems with heat and my ICM going bad. After burning out 3 of them I posted here finding help and someone advised to get the stuff from radio shack in the little tube. ( heavy duty Heat shrink) I have not had a problem with the car not starting. knock on wood
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