Here we go again
Thread Starter
Le Mans Master
Joined: Jul 2009
Posts: 6,381
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From: SF bay area C.A.
C4 of the Year Finalist
Here we go again
As you may know I broke down last Sunday Which makes only 3 years since my last tow. After a few days I went to start her up and she started so I let her run until operating temp. At around 194 degrees the rpms started to roll and she quite and did not start again. It looks like a heat related problem and time to check the icm and the mounting grease[ forget what type it is] and I'm open to any new suggestions.
Race Director
Joined: Mar 2015
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As you may know I broke down last Sunday Which makes only 3 years since my last tow. After a few days I went to start her up and she started so I let her run until operating temp. At around 194 degrees the rpms started to roll and she quite and did not start again. It looks like a heat related problem and time to check the icm and the mounting grease[ forget what type it is] and I'm open to any new suggestions.
also let it cool down then see if it starts. Then when hot if no start change your coil too.
Thread Starter
Le Mans Master
Joined: Jul 2009
Posts: 6,381
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From: SF bay area C.A.
C4 of the Year Finalist
Yeah I'v gone through this before and it seemed like 50% of the icm did not work correctly. I also think I am losing my memory dont remember what type of grease to use.
Instructor
Joined: Nov 2012
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From: Long Island
Race Director
Joined: Oct 2011
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
I like to see if it's opti or not when an LT1 turns off on me. Connect noid light to fuel injector number one. While cranking, if no light, opti is bad. But yes, I'd re apply the thermal grease.
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Thread Starter
Le Mans Master
Joined: Jul 2009
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From: SF bay area C.A.
C4 of the Year Finalist
It's not the opti, I can go out and it will start right up. When it gets hot[operating temp] the rpms start to roll and she quits and won't start until she cools down. When my opti took a nose dive it would never start.
Race Director
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
Thread Starter
Le Mans Master
Joined: Jul 2009
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From: SF bay area C.A.
C4 of the Year Finalist
I just took off the old coil and icm and I must say there was not much grease on the head or the back of the icm so will try some new ones I have. As far as the grease goes is die electric ok or should I get a heat sink product?
Burning Brakes
Joined: Jul 2013
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From: Granite City Illinois
Myself I would for sure get thermal grease and some people say use a thick coat, but usually you want a thin coat just to fill in minor irregularities, since the grease doesn't conduct heat as well as metal will. Too thick you could be in the same boat as none.
Team Owner
Joined: Aug 2004
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From: Park City Utah
Video here:
If you have a tach signal when it's hot and won't start, either checking by injector pulse as mentioned above, tech reading on a scan tool, or just watching the tach while cranking, then the Opti is not the problem.
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Le Mans Master
Joined: Jul 2009
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From: SF bay area C.A.
C4 of the Year Finalist
Wow that was a great write up and a lot of work. I already have the icm on a shelf so I will try that first. If still a problem I will follow your procedure. Funny you brought up the plug connectors for the coil/icm because last time I had this problem it was the black plug that was bad, replaced it and has been fine until now. Thanks again.
Burning Brakes
Joined: Jul 2013
Posts: 1,027
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From: Granite City Illinois
It COULD be the opti. It's more likely that it's the ICM...but the opti can die from heat, and I PROVED IT HERE.
Video here:
large - YouTube
If you have a tach signal when it's hot and won't start, either checking by injector pulse as mentioned above, tech reading on a scan tool, or just watching the tach while cranking, then the Opti is not the problem.
Video here:
large - YouTube
If you have a tach signal when it's hot and won't start, either checking by injector pulse as mentioned above, tech reading on a scan tool, or just watching the tach while cranking, then the Opti is not the problem.
I was going to say something about Tom coming in soon on that one
Melting Slicks
Joined: Sep 2003
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From: N. Babylon NY
When I was trying to figure out my problem I just connected a new ICM without mounting it. Did the same with the coil. Connected them with the engine at running temp. In both cases it did not fix my problem. In my case it was the wires and plugs (if you followed my thread).
Good luck and please report your fix.
Good luck and please report your fix.
Thread Starter
Le Mans Master
Joined: Jul 2009
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From: SF bay area C.A.
C4 of the Year Finalist
Update. Well I removed the old icm and cleaned everything up. Put heat sink grease behind the new icm and on the head, turned it on and let it run & run & run. It idled at operating temp for about a half a hour or until my wife shouted to me to shut it off because she was trying to sleep. So I took it out on the road and everything seems fine for now. I'll cross everything I can cross on my next drive. 
Race Director
Joined: Oct 2011
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
Update. Well I removed the old icm and cleaned everything up. Put heat sink grease behind the new icm and on the head, turned it on and let it run & run & run. It idled at operating temp for about a half a hour or until my wife shouted to me to shut it off because she was trying to sleep. So I took it out on the road and everything seems fine for now. I'll cross everything I can cross on my next drive.
