1999 Jeep Laredo coil pack problem?

Tiny
SD1455
  • MEMBER
  • 1999 JEEP LAREDO
Engine Performance problem
1999 Jeep Laredo 6 cyl Four Wheel Drive Automatic 150k miles

got #1 misfire code Had code cleared and tune up done at shop. Ran good for a week. Drove in rain and check engine on again. #4 misfire code. Now runs rough with sputtering 45-55 mph. No power uphill. Coil pack not changed at tuneup. Wondering if this could be problem
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Tuesday, October 27th, 2009 AT 5:20 PM

8 Replies

Tiny
MHPAUTOS
  • EXPERT
HI there,

Could well be a faulty coil, you can test with a multi meter but often they do test ok and start to break down when they heat up, a run on an oscilloscope can help track down faulty coils.

Mark (mhpautos)
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Tuesday, October 27th, 2009 AT 7:00 PM
Tiny
SD1455
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Disconnected battery to clear codes. Changed coil packs. Seems to run a little better still sputters @ 45-55 mph No engine codes come up. Read somewhere that car may have to "relearn" shifting after disconnect. How long does that usually take
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Wednesday, October 28th, 2009 AT 5:14 PM
Tiny
MHPAUTOS
  • EXPERT
HI there,

I would have to check this for your car, but normally any re learn will take place after a few drive cycles, I will look into it for you, but it will take a few days as I am away no a training course as of this after noon for a few day.

Mark
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Wednesday, October 28th, 2009 AT 5:21 PM
Tiny
SD1455
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Still idles rough. Came to a stop and it stalled. Drove some more and got #4 misfire code. New plugs, coil packs, fuel filter, o2 sensor. Maybe bad injector?
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Wednesday, October 28th, 2009 AT 10:43 PM
Tiny
MHPAUTOS
  • EXPERT
Could be, but I would be checking for a vacuum leak as well, I could not imagine all 4 injectors going at once, have you checked for bad fuel?

Mark
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Wednesday, October 28th, 2009 AT 11:07 PM
Tiny
SD1455
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Havent found any vacuum leaks
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Wednesday, October 28th, 2009 AT 11:12 PM
Tiny
SD1455
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Brought back to shop. Found 4 of the 6 plugs with cracks in ceramic. Changed plugs and runs good again. Hopefully more than a week this time. Thanks for the replies
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Thursday, October 29th, 2009 AT 5:02 PM
Tiny
SD1455
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Takes 3 times to start in morning. Stalled twice yesterday when at a stop.
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Tuesday, November 3rd, 2009 AT 11:24 AM

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