Jeep jerking like a misfire, code P1391
 

Hi all,

2000 XJ, 210k miles (~170k on the engine), auto trans 4x4

A few weeks ago I was towing my jetski down the shore, about 75 miles one way, when I felt a few random jerks while driving. Pretty much like a dead miss but just one and then nothing for a while. Only happened maybe 5 times total on the whole trip.

Just took it to the store however, maybe a 15 miles round trip, and it was doing it alot more. It definitely feels like a misfire, it idles fine but under load it jerks and rpms bounce. The CEL came on on my way home, only code is P1391. I know for sure the CKP and CMP can cause misfires, but any way to tell which one it is? or just replace both?

Did you find solutions mine is doing the same. Brand new crank and came too

Hey, yea it turned out to be the crank position sensor even though it wasn't that old. I replaced the parts store one with a Standard Motor Products one from rockauto. It's been in since last November with no problems, so I guess I'll see how long it lasts. If you have the cash they have actual Mopar sensors for $85.

There are three sensors on the Jeep where you should not even THINK about using any aftermarket sensors:

1. Crankshaft position sensor
2. Camshaft position sensor
3. O2 sensor

Stick with Mopar or NGK (who actually makes Mopar's sensors), or risk anything from out of box failure, to weeks or months later. OR worse, they won't outright fail but will just never let your engine run correctly.


Better yet, just still with the good stuff for all sensors.