RTH - Off-idle/on-throttle stumble (1 Viewer)

cruiser100

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100 threw a code - bad coilpack #4 cylinder - a couple of weeks ago. I replaced the coilpack and now have an off-idle/on-throttle stumble, no codes.

I reseated all the coilpacks, checked connections to packs, reset computer. MAF sensor and TB we're cleaned a couple of months ago and plugs are less than a year old.

Any ideas?
 

cruiser100

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Same symptoms as before you replaced the coil pack?

Nope. With the bad coil pack there was a constant miss at speed and at idle. With this issue, once you get past the initial stumble the truck runs fine and idles fine. May try pulling the plugs to have a look...
 

cruiser100

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I was wondering about another coil pack as well - may be possible its starting to go just hasn't given up the farm yet. I hear when the first one goes you should get ready for more.

I replaced the FF a couple of years ago but it wouldn't hurt to check it...
 

cruiser100

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Yeah, I was just thinking about biting the bullet and replacing them all - it'll get one thing out of the way.
 

cruiser100

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Just following-up on this - found the problem. It would seem that a sparkplug had backed out far enough to "unseal" the combustion chamber.

I changed plugs about a year ago and evidently didn't get one tightened down well enough... :bang:
 
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Similar issue on ours at one point. Had the spark plugs changed at 93k and next morning car idled rough and stalled. Turns out we had a bad spark plug and the dealer replaced all eight for free.
 

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