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post #1 of 13 (permalink) Old 05-24-2016, 06:25 AM Thread Starter
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Running Rough at Idle No Communication with OBD II

Like the title says wife's car (05 cobalt LS 2.2L auto) is misfiring (sort of like a sputter at idle. No CEL. Go to hook up my code reader. It powers up but no communication.
Also I pulled intake and throttle body and cleaned (even though it really wasn't dirty).

Not sure where to go from here.
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post #2 of 13 (permalink) Old 05-24-2016, 07:04 AM
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Joined in July of 2011 and this is your first post? Wow, professional lurker!


I'd probably say check the spark plugs and the coil pack first.


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post #3 of 13 (permalink) Old 05-24-2016, 07:12 AM Thread Starter
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Yea I know. I usually fix the problems using search function

I pulled the plugs yesterday they were fine (they only have 20000 on them). They were light gray. Is there a way of testing the cassette type coil pack?

Thx
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post #4 of 13 (permalink) Old 05-24-2016, 07:35 AM
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You can check for cracks or arc burns but only real way to check the coil pack is to replace it. If it's never been changed chances are it's due.

I believe the key has to be turned to accessory for the PCM to communicate with the OBDII port and the 05-06 is not compatible with Candi module readers.

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post #5 of 13 (permalink) Old 05-24-2016, 07:42 AM
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Did you happen to check the plug gap? They've got pretty small tolerances.

I've never had to do it, so I don't know for sure this is a good method, but this is what I got from Googling it:

How to Troubleshoot an Ecotec Ignition Coil


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post #6 of 13 (permalink) Old 05-24-2016, 07:44 AM
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Quote:
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You can check for cracks or arc burns but only real way to check the coil pack is to replace it. If it's never been changed chances are it's due.

I believe the key has to be turned to accessory for the PCM to communicate with the OBDII port and the 05-06 is not compatible with Candi module readers.
Is there a timeline on changing them? Or just when they may be a problem? I'm at 173,000 miles on originals.

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post #7 of 13 (permalink) Old 05-24-2016, 07:46 AM Thread Starter
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Ok i'll grab a new one on the way home tonight. Ill also check plug gaps.

Thx for the reply i'll report back with the results.
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post #8 of 13 (permalink) Old 05-24-2016, 08:42 AM
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Is there a timeline on changing them? Or just when they may be a problem? I'm at 173,000 miles on originals.
I don't see anything about the coil pack on the Recommended Maintenance Schedule thread. If you're not having a problem, it's probably fine. If there's a misfire, or just rough idle, you might replace them next time you replace your spark plugs.


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post #9 of 13 (permalink) Old 05-24-2016, 09:02 AM
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Like anything else some last for ever some die prematurely. They have been problematic and are often the cause of erratic misfire and rough idling. As far as gap be very careful with the dual iridium plugs, they come pre-gapped and are easy to damage because of the little iridium piece that's welded to the electrode. ( You can barely see it )


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post #10 of 13 (permalink) Old 05-25-2016, 07:50 AM
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Quote:
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I don't see anything about the coil pack on the Recommended Maintenance Schedule thread. If you're not having a problem, it's probably fine. If there's a misfire, or just rough idle, you might replace them next time you replace your spark plugs.
I just put my second set of plugs in at 160,000 miles. Those coil packs are fairly inexpensive, like $26 and change on rockauto. I've noticed a slight stumble or misfire at idle so maybe I'll replace them and see if it helps.

I guess the AC Delco's are the best to get?

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