P1391 Help

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12-07-2022, 03:44 PM

spencerjacobson

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Join Date: Oct 2021

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Year: 1999

Model: Cherokee (XJ)

Engine: 4.0L

P1391 Help

My 99 XJ with the 4.0 is currently throwing the P1391 code for intermittent loss of CMP or CMK. CEL and code showed up after both battery terminals were replaced due to the car receiving 0 power. The car has a slightly rough start when its cold outside but will still always start. Noticed today that my RPMs were dropping by about 200 every once in a while when it was warming up but seemed to drive fine once it was warmed up a bit. I've recently replaced the crank sensor with one from the dealership and over the summer I replaced my cam sensor, spark plugs, distributor cap and wires, and crank sensor wiring. Any ideas on what could be causing this? Wondering if it could be fuel related, the throttle position sensor or the idle air control valve? Thank you.

Last edited by spencerjacobson; 12-07-2022 at 04:02 PM.

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12-07-2022, 06:07 PM

awg

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Year: 96

Model: Cherokee (XJ)

Engine: 4.0

a couple of years ago there was a long thread on this, the guy bought an oscilloscope and everything, but I cant remember what the solution was

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