: Mechanic needs help, NS killing ICM



Capn Hook
02-12-04, 03:21 PM
Lo Folks,

Just completed a head gasket job on 94 Northstar. Before I
started the job the engine had a miss, I chalked it up to the
blown gasket.
But the miss is still there. this apparantly was a pre-existing
condition. I know what is happening, I just don't know why!!!

A quick check of the coil packs showed me that cylinders
1 and 4 were not firing. I checked the ICM terminals where the
coil pack plugs in and I have power and a ground. I replaced the
coil pack. Same problem, no spark to 1 and 4.

I then replaced the ICM and bingo! I had spark to 1 and 4.
I shut the vehicle off and when I restarted it several minutes
later, the engine is missing again. And again I have lost spark to
1 and 4.
Then I give the vehicle to my electrician and he spends several
hours checking the signals from crank sensors A and B, cam sensor
signal etc, etc. Then he installs another new ICM and once again
we are hitting on all eight.
I bring the vehicle back to my stall and button it up as it
pertains to splash shields etc. When I restarted the car, again it
loses 1 and 4.
For some reason this car is smoking Ignition Control Modules.
Although I have power and ground at the coil pack terminals I
am losing the trigger signal to collapse the field in the coil. At
one point I did throw a PCM at it to try and bring those cylinders
back, to no avail.
Anybody have a clue? Thanks in advance for any help.

Sincerely,
Brian K. Ballard

Anthony Cipriano
02-13-04, 04:15 PM
Lo Folks,

Just completed a head gasket job on 94 Northstar. Before I
started the job the engine had a miss, I chalked it up to the
blown gasket.
But the miss is still there. this apparantly was a pre-existing
condition. I know what is happening, I just don't know why!!!

A quick check of the coil packs showed me that cylinders
1 and 4 were not firing. I checked the ICM terminals where the
coil pack plugs in and I have power and a ground. I replaced the
coil pack. Same problem, no spark to 1 and 4.

I then replaced the ICM and bingo! I had spark to 1 and 4.
I shut the vehicle off and when I restarted it several minutes
later, the engine is missing again. And again I have lost spark to
1 and 4.
Then I give the vehicle to my electrician and he spends several
hours checking the signals from crank sensors A and B, cam sensor
signal etc, etc. Then he installs another new ICM and once again
we are hitting on all eight.
I bring the vehicle back to my stall and button it up as it
pertains to splash shields etc. When I restarted the car, again it
loses 1 and 4.
For some reason this car is smoking Ignition Control Modules.
Although I have power and ground at the coil pack terminals I
am losing the trigger signal to collapse the field in the coil. At
one point I did throw a PCM at it to try and bring those cylinders
back, to no avail.
Anybody have a clue? Thanks in advance for any help.

Sincerely,
Brian K. Ballard


Did you try a different coil on for those cylinders? It sounds like the coil may be shorting and drawing too much current for the ICM. I know you mentioned replacing the "coil pack" but then this didn't fix the problem. when you replaced the ICM did you use the original coils or the new ones?

The PCM has no idea which cylinder is firing so it is not likely the PCM. If the crank sensors are reading and the ICM is deciphering the signals from the crank reluctor ring correctly (which it is if it is firing at all) then it is not likely in the crank sensors I wouldn't expect.

I would suspect the coil at that location or a bad plug wire or plug. Did you check the plug gap? Possible the wrong plugs/misgapped plugs are in the engine causing enough current draw on the 1/4 coil to kill the ICM for those cylinders.

Capn Hook
02-15-04, 08:52 AM
Thanks for the info. Yes I did try a new coil but the ICM
was already smoked. For Monday they are getting me
new coil, ICM and plug wires, this should fix it. They also
ordered both crank sensors but I agree with you, the
car does run so the sensors must be working. Thanks
again for everyones help.

Capn Hook

Anthony Cipriano
02-16-04, 12:06 PM
Thanks for the info. Yes I did try a new coil but the ICM
was already smoked. For Monday they are getting me
new coil, ICM and plug wires, this should fix it. They also
ordered both crank sensors but I agree with you, the
car does run so the sensors must be working. Thanks
again for everyones help.

Capn Hook
Yes, if you hadn't tried a new coil with a new ICM then that should show some improvement. Let us know what you find.