V6 Tech 1967-2002 V6 Engine Related

V6 3.8L Rough Idle Need Help!

Old 02-11-2013, 11:30 AM
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V6 3.8L Rough Idle Need Help!

Well I was troubleshooting my friends vehicle and came to the conclusion that one of his coil packs was bad. I moved the suspected coil pack and the problem followed. So I instructed him to R2 it, the problem came back. Immediatly I assumed the new "rebuilt" pack was DOA so I had him RMA it. Problem is still there with 2nd coil pack. Anything I can look for ? Or is DOA packs the norm?

For trouble shooting I checked the signal coming out of the packs(plug wires) and the affected pack was inntermittent in firing. When I moved the pack from the rear to the front the problem followed.
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Old 02-11-2013, 09:58 PM
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Re: V6 3.8L Rough Idle Need Help!

Update*

I have continued to troubleshoot. We ruled out plugs and wires with the coil pack swap. As the moved coil pack moved the missing cylinders.

I ruled out fuel as I have tested the pressure per the manual and it does not drop more than 7 psi from initial prime and is running a good 42 psi @ idle.

Now we have gone to a different brand of coil pack with no results. Same cylinders missing.

I am having him try one more pack before buying one from the dealer. (crosses fingers)

Has anyone else had this luck? I read through the miss fire sticky to note a small trend with this and wires going bad. Those just where changed prior to my troubleshooting.

I did note some "chaffing" on one of the injector leads but isolating did not improve idle.
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Old 02-13-2013, 11:07 AM
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Re: V6 3.8L Rough Idle Need Help!

Some more trouble shooting yesterday,

R2 the "faulty" coil pack once again, and idle drastically improves.
Still feel a miss here and there but not both cylinders firing off half the time.
Going to look at the plugs today to see if the missing maybe fouled them up.
With the failing cylinders moving with the coil pack I am pretty stuck on it being the problem.

From the sticky I got multiple things could cause this(as did the shop manual)
We have checked everything minus the PCM. Would this faulty PCM cause the failing cylinders move with the coil pack? My next step would be ohming out the coil packs and the pcm?
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Old 02-17-2013, 09:35 PM
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Re: V6 3.8L Rough Idle Need Help!

Originally Posted by chevy_dude97 View Post
Some more trouble shooting yesterday,

R2 the "faulty" coil pack once again, and idle drastically improves.
Still feel a miss here and there but not both cylinders firing off half the time.
Going to look at the plugs today to see if the missing maybe fouled them up.
With the failing cylinders moving with the coil pack I am pretty stuck on it being the problem.

From the sticky I got multiple things could cause this(as did the shop manual)
We have checked everything minus the PCM. Would this faulty PCM cause the failing cylinders move with the coil pack? My next step would be ohming out the coil packs and the pcm?
does it show multiple misses detected?
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