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Stumbles on acceleration, backfires or pops under load

Tiny
JAMES FRANCIS
  • MEMBER
  • 2003 DODGE CARAVAN
  • 164,508 MILES
Caravan starts & idles & runs ok at speed; code reader gives misfire on cyl 2 Took out plug 2 to find it coated with black soot. Put back in. Checked plug wire by replacing with a similar one. Ran same with continued pop and backfire? Replaced orig plug wire. Next day exchanged plugs between 2 and 4. Plug 2 this time was nice and gray like #4. Went to Advance to check their code reader against the one I borrowed and got the same code: misfrire on #2. Seemed to get worse on the 6 mile trip home. Help. Must be the coil pack?
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Thursday, May 3rd, 2012 AT 9:23 PM

3 Replies

Tiny
PROMECHANIC
  • MECHANIC
  • 536 POSTS
Could be the coil pack. But it could be an internal problem with the cylinder too, like worn valves causing low compression. I would get a spark tested and see if that cylinder is losing spark. If it is, then it could be the coil pack. If not then I would check the compression to make sure the engine is not worn internally.
Another thing it could be is the injector. You might try swapping to see if they problem follows the injector.
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Thursday, May 3rd, 2012 AT 9:29 PM
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
I have to guess which engine you have but if it has a coil pack, it must be the 3.3L / 3.8L. They had a problem in the early '90s with bad plug wires causing backfiring on acceleration. The best bet is to just replace the entire set, especially if they original.
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Thursday, May 3rd, 2012 AT 9:30 PM
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Sorry promechanic, I was already busy typing while you were posting. Swapping injectors is an easy way to identify a bad one, but Chrysler has extremely little trouble with theirs, especially compared to GM, so those should be the last thing to suspect. There were a few problems with coil packs too years ago, but that should cause two cylinders to misfire unless there is arcing taking place right at the plug wire connection. That would also be pretty uncommon.
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Thursday, May 3rd, 2012 AT 9:35 PM

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