Sudden misfire, tach died, no codes. ICM? (Page 1/1)
cebix JUL 16, 03:06 AM
'85 duke auto w/AC

Had a weird situation today. While accelerating hard in first gear at high revs I heard a bang and had a sudden misfire. No action above say 1/5 throttle, would sputter and want to die, idled good though. Noticed the tach was jumping all around until it dropped to a dead 0. Car was still running, no check engine light, occasionally would sputter at idle too. Shut it off, didn't see anything in the engine bay, wiggled around some connectors, started the car again and it runs normal again, tach works, no codes stored.

Any ideas what could have happened? Are these bad ICM symptoms? Could it have been in some limp home mode? Could a bad connector on the ignition coil cause engine running poorly with no tach but still run?
Patrick JUL 16, 03:30 PM

When an ICM is starting to fail, it will often appear to be operating normally again when it cools down. However, once it heats up, it then craps out again. My experience with this is Here.
Will JUL 16, 03:46 PM
Tach filter?
Frenchrafe JUL 16, 03:55 PM

quote
Originally posted by Patrick:


When an ICM is starting to fail, it will often appear to be operating normally again when it cools down. However, once it heats up, it then craps out again. My experience with this is Here.




Ditto
Had the same symptoms on an Ignition Control Module.
Regards,
Rafe

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
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cebix JUL 17, 02:48 AM
Can't replicate the problem. It started right up after shutdown yesterday, so I guess it didn't cool down much.

I think it's a loose connector to the coil. Could unplugging one could make the car still run but the tach read zero? I have a spare ICM, so keeping that with my now on the car just in case.
sledcaddie JUL 17, 12:29 PM
I think I remember seeing on here (and using) that if engine doesn't run, but tach moves while cranking, it is the ICM. If the tach doesn't move, it could be the coil or something else.
(I think I got this right. If I have it backwards, let me know.)
Gall757 JUL 17, 03:25 PM
....you got it backwards. A moving tach tells you the ICM is sending pulses to the computer.