ICM failure again!!
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
Good luck - I haven't found a solution yet.
One thing I did that helped a little was putting a couple of washers between the head and the heat sink.
I even tried AC/Delco instead of the ones I was getting from the auto parts stores.
One thing I did that helped a little was putting a couple of washers between the head and the heat sink.
I even tried AC/Delco instead of the ones I was getting from the auto parts stores.
Thread Starter
Pro
Joined: Sep 2004
Posts: 505
Likes: 1
From: Guntersville Alabama
93cruiser
Thread Starter
Pro
Joined: Sep 2004
Posts: 505
Likes: 1
From: Guntersville Alabama
I have check the fcm. Let me see if I understand. The fried ECM circuit for the ccp could have damaged the ECM as it relates to the ICM. Is it that about right?
Pro
Joined: Aug 2009
Posts: 725
Likes: 4
From: Plano, TX
I think your problem could be caused by a short at the connectors. They are not very weatherproof like the newer connectors and they begin to arc. You might consider upgrading to the 96 ICM. Which will require you to upgrade the connectors to the newer style too. Alot of the Fbody guys did this with good results. Never tried it on a corvette. I had problem with my icm on my 93 too. My solution? Accel gen 7 computer with an old school rear mount distributer and small block coil. A little heavy handed but it worked. LOL
Last edited by 93VettePilot; Jan 31, 2011 at 10:39 PM.
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Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
The ICM is nothing more than an amplifier. It is driven by a 5 volt p-p square wave from the ECM. It develops about 70 v p-p waveform output to drive the primary of the coil. The coil is about the only thing that could draw additional current from the ICM. You might want to consider changing your coil on a chance. I don’t think spark plugs would cause your problem.
The other issue is heat sinking it correctly. From what I remember it goes flush against the head. If you stand it off with washers you will not get proper transfer of heat from the ICM to the engine.
However going out on a limp, if your electrical system had spikes it may affect the ICM. Like if you lost a phase from the alternator. But that is a real stretch, but just info for you and thought.
A lot of vetts run hot and 15* higher should put you at 215-220. That range is within tolerance and normally should not cause a problem.
The other issue is heat sinking it correctly. From what I remember it goes flush against the head. If you stand it off with washers you will not get proper transfer of heat from the ICM to the engine.
However going out on a limp, if your electrical system had spikes it may affect the ICM. Like if you lost a phase from the alternator. But that is a real stretch, but just info for you and thought.
A lot of vetts run hot and 15* higher should put you at 215-220. That range is within tolerance and normally should not cause a problem.
Advanced
Joined: Jan 2002
Posts: 87
Likes: 0
From: Auburn WA
The ICM and ignition coil mount bracket should have heat sink compound applied to the side that attaches to the engine. That is the way it came from the factory and the FSM specifically mentions it. If you do not use the heat sink compound, then engine heat will drastically shorten the life of the ICM. Spacing the bracket away from the engine by using washers or spacers is not kosher and will not have the desired effect. The only store at which I have been able to find heat sink compound is Radio Shack.
Thread Starter
Pro
Joined: Sep 2004
Posts: 505
Likes: 1
From: Guntersville Alabama
Thanks for the suggestions. I have been looking at the fsm. I might find a DTC42 code. I will check this when it stops raining. I believe this to be an intermittent problem though. I will check the carbon canister solenoid as well. I believe that it is not working quite right. If it turns out to be an intermittent short at the ECM connector, what are the chances of installing a fuse at the icm protect it from getting fried?
Thanks,
93cruiser
Thanks,
93cruiser
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
The ICM and ignition coil mount bracket should have heat sink compound applied to the side that attaches to the engine. That is the way it came from the factory and the FSM specifically mentions it. If you do not use the heat sink compound, then engine heat will drastically shorten the life of the ICM. Spacing the bracket away from the engine by using washers or spacers is not kosher and will not have the desired effect. The only store at which I have been able to find heat sink compound is Radio Shack.
I don’t see any relationship between having a problem with the charcoal canister purge solenoid and having ICMs going bad. I can see where a solenoid could affect the ECM if it would draw to much current. Although don’t know if a solenoid could burn a land up however that is a separate and different issue. The problem here is losing ICMs.
I would first start by properly mounting a new ICM with plenty of heat sink grease. Then if problems persists troubleshoot further.
Melting Slicks
Joined: Jul 2006
Posts: 2,151
Likes: 0
From: Strongsville Ohio
I am on my third as well. I pulled a code that would flash ONLY when I hit the gas which was weird but anyway. Said that I had a bad ICM ground connection.
Have not found the ground connection to be bad. Once I get the motor back in and running I will post if I have any problems. I would love to perm. fix this issue
Have not found the ground connection to be bad. Once I get the motor back in and running I will post if I have any problems. I would love to perm. fix this issue
Thread Starter
Pro
Joined: Sep 2004
Posts: 505
Likes: 1
From: Guntersville Alabama
I don’t see any relationship between having a problem with the charcoal canister purge solenoid and having ICMs going bad. I can see where a solenoid could affect the ECM if it would draw to much current. Although don’t know if a solenoid could burn a land up however that is a separate and different issue. The problem here is losing ICMs.
I would first start by properly mounting a new ICM with plenty of heat sink grease. Then if problems persists troubleshoot further.
93cruiser
Burning Brakes
Joined: Nov 2009
Posts: 828
Likes: 103
From: Olney MD
ICM Troubleshooting
My 93 vert is running like crap (no power, backfiring on acceleration) and i just replaced the coil and plug wires. I thought OPtispark was next step, but if the ICM could go bad and cause my symptoms I'd do that instead of the dreaded Opti.
Thanks
Paul
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
ICM generaly fail eailry do to high restance in plug wires, coil, or plugs, This is the first place I would look. I would go as far as replacing plugs and wires if it has been awhile.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
If you fail a ICM put a coil on it. There are only 2 common ways to fail the ICM, heat and too much current. The heat sink mod of spacers will kill lack of heatsink compoung will kill and a coil that is partially shorted or the wrong coil for the ICM will kill it as well.
Dave
Dave
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
I have a question-How do you know your ICM is bad?? Does it set a code or is there a well known symptom?
My 93 vert is running like crap (no power, backfiring on acceleration) and i just replaced the coil and plug wires. I thought OPtispark was next step, but if the ICM could go bad and cause my symptoms I'd do that instead of the dreaded Opti.
Thanks
Paul
My 93 vert is running like crap (no power, backfiring on acceleration) and i just replaced the coil and plug wires. I thought OPtispark was next step, but if the ICM could go bad and cause my symptoms I'd do that instead of the dreaded Opti.
Thanks
Paul
If so tell us the codes
Check the wire bundle from the opti to the ecm connector on the passenger side of the intake. The ICM will not set a code - usually
Burning Brakes
Joined: Nov 2009
Posts: 828
Likes: 103
From: Olney MD
ICM Suspicions
I did check ICM - testing A and D (on the ICM plug) with a multimeter to ground, and both came up at 11.6 volts. I have not done the AC voltaqe test with a helper cranking the engine. I'll try that tonight.
I've replaced plugs and wires AND Coil! I'm doing everything I can to make sure that if I get down to replacing the Opti, then that will in fact get me running again.
I've visually checked hoses for vacuum leaks, and see none.
Please tell me it's not the dreaded Optispark!
