First post here....came looking for answers. I've had several Jeeps, this is the only XJ and is my daughters.


Lifted 6 1/2 0n 35's 4:56 gears butIt's a stock motor. 2000 classic.




It's been doing this misfire, acts like it's tripping over itself. Kind of hard to describe, I guess maybe bucking a bit and rough idle. Pulled codes for coil pack and Crankshaft sensor. Swapped those both out. OEM sensor, no aftermarket crap. All new plugs as well. Still no fix.


I've read thru some of the threads on here and will be checking the motor mounts and tcase mounts, but what else am I missing??? It's not an offroad jeep so doesn't get all the sand or dirt in to be too concerned dirty MAS.


perfect pressure at fuel rail as well.


I'm stumped and would like this ready for her to drive when she gets back from school for the holidays. Help please!

 

Regeared for 35s but no offroad? Tsk tsk tsk...

First thing I'd do is go looking at wiring. Generic problems with codes for not-really-related systems normally are chafes, shorts, or bad grounds.

Has P0340 ever appeared?

 

yes yes I know..tsk tsk.....It was meant to get lockers so she could follow me around the parks, but I ended up selling my money pit on 42's and getting the 2014 Rubi. ( which now has 35's as well...lol)


I HATE WIRING! But yea, seems to be everyone's first thoughts. I don't remember that code popping up .....but it very well may have in the weeks we have been troubleshooting. going to look at the ground wires today....

 

Post the exact codes here. With OBD, the devil is definitely in the details.

 

Buddy with computer heading over in a bit. i'll post them when he gets here.

 

Codes are :


P1391
says probable cause : timing chain stretched or jumped or defective CMP sensor


P1899
probable cause: failed park/neutral switch or open/shorted circuit condition

 

1. I'd start with the P1391, which can be related to either the crank sensor circuit or the cam sensor circuit. I'd begin with testing of your cam sensor. You'll need a meter and a manual. Sometimes you need to actually reindex this sensor (toothpick technique; search). I don't think this is a stretched timing chain.

2. The P1899 is most likely related to your neutral safety switch, a common issue with the 4.0. This switch can be cleaned, regreased, reassembled and adjusted and may take care of your problem. Here is a link to that procedure.

http://bc4x4.com/tech/2010/jeep-neut...ty-switch-nss/

Good luck and keep us posted!

 

I'll look that up and see if it's something I can tackle.....the Crank senser is new...OEM.....so my guess was Cam sensor as well. I get 10% above cost so was just gonna grab one......


As for the neutral switch, what I read on that was more of a non starting issue. ???? Jeep starts fine.

 

More searching leads to a multitude of people with the same issue.......some have replaced a ****ton of parts. a couple said they disconnected the battery to reset and a couple others replaced the distributor itself.....and it cleared the issue. Said the cell is known to go bad. ????


I guess I should have mentioned the motor has 150,000 miles on it.....maybe that makes a difference...idk

 

2000 and 2001 cherokees are distributorless unless a PO changed the motor you have no distributor. I suppose we should double check this is a 4.0 and not the 2.5 right, there were a few 00 and 01s with the 4 popper.

 

yea, I wanna say it was a 96 in the thread I was reading. It's a 4.0.


My eyes hurt from searching for answers. I have some tools and some know how and a husband that can fix or build anything but cars...lol. ordering cam sensor....going from there.....

 

A trouble code identifies an issue in an emissions control circuit, not necessarily a specific component. If it's a wiring issue replacement won't fix it. It would be less expensive to test the old one first.

 

Agreed.


Actually handing the project over to a friend of mine that is a Chrysler mechanic and owns the identical Jeep. It's beyond my comfort zone, knowledge and tool list at this point.


Thanks for the input and I will keep the thread posted as to what we find

 

When my 01 XJ was misfiring it was low compression from a problem with the valve seats. Rebuilding the head fixed the problem.

If you still have it, I'd do a compression test.

I too changed the crank, cam, and ignition coil rail with dealer parts. With my buddy and I scratching our heads, I took it to a good shop who diagnosed the problem in about an hour.

Please note, as this is a 2000 and probably has an 0331 with high rate of cracking because of a weak casting, if the head does come off, please do yourself a favor and replace with a Clearwater, Alabama, or junkyard factory 0331 TUPY head...

I ended up replacing my rebuild head about 6 years later because it cracked.

I didn't know as much about Jeeps back then.

 

Shipped it out to a trusted name in my area and the Jeep community over here. He is positive he can get to the bottom of the issue. My limited knowledge and tool base....and time...have been surpassed. AAA dropped it at his shop this evening. It's like waiting for test results at a hospital...nerve racking.