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04 CTT Rough Idle after 20 minutes of driving.

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My 04 CTT started idling rough after driving for 20 minutes or so. On cold start up (i live in AZ so its not that cold) the car runs great for 20 minutes or so then it begins to idle really rough and seems to have less power at low RPM's. At higher RPS's the issue goes away. The Check engine light came on then went off and now it is back on again. Anyone have an idea as to what the issue is here?



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Can you read the code? Another possibility is the coils packs.  Happened to me.  About 20 mins of driving, my Cayenne started driving rough. I can't recall the code number, but it was misfire in cyl 2.

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agreed it sounds like either a pump or a coil.


Drive the car until it warms up/starts to run rough.

pull all 8 plugs and see if there are a few that look much different than the others.  If there are then you got some bad coils.

If they all look the same, my guess is the fuel pump.....you can jumper it and then listen to it unde the rear seat.....the sound is obvious when it's going bad.

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