2000 cherokee rough idle

DLOR

Well-Known Member
Joined
May 13, 2007
Location
Chapel Hill
i am having trouble with a 2000 cherokee 4.0 auto. 132343 miles. it has a rough idle and almost lopes like it has a cam in it. it sputters on acceleration and under load going uphill. also a p0302 keeps coming up. the higher the rpms the smoother it seems to run. i feel it may be off in the timing but not sure how to check that. it had a cracked head and low oil pressure when i got it. i bought a new head from clearwater on fleabay and had a complete running 1999 xj for parts. i swapped the head onto the the 99 block and this is where i am now.
things i have done:
checked #2 injector and swapped it with #3
voltage at #2 is 13.67V, checked continuity and wire harness between the injector and the pcm on the ground side is good.
set the cam sensor using toothpick method at #1 tdc
replaced the following sensors with ones form the 99:
TPS, MAP, IAC, ECT, ITS, CKS, new front o2, the entire cat back, and cleaned the throttle body
i have a crappy scanner and these are the results at idle
fuel psi: 48psi (with gauge)
manifold vacuum: 16-17iHg (with gauge)
engine rpm: 682-703 rpms
TPS: 17%
ECT: 203 Deg F
Intake Air Temp: 126 Deg F
O2 sensor 1/1: .06-.08V
O2 sensor 1/2: .82-.94V
Spark Advance: 4-6Deg
Calc Engine Load: 4.7%
Fuel Sys Status: Closed
long term f/t: 7.8%
MAP: 12iHg

Not sure if any of these are within spec. any help would be greatly appreciated.
thanks kelsey
 
Have you pulled the plugs and looked at them. Are you running the coil on plug system. It could be a bad coil.
 
yeah I checked the plugs, they all looked good. they were brand new ngks when I did the head. it does have the coil on plug rail. it might be one of the coils, but not sure how to test it?
 
I did swap it. both jeeps ran fine before the meshing of the two engines, minus the coolant loss in the 2000. that's why I thought it might be the timing? I don't know how to check it bc my timing light doesn't work with the coil on plug to check it. is 4-6 deg spark advance about right? or it could be the coil rail or the cam sensor?
 
good thoughts, keep them coming! I know there are some jeep guru's on here lurking
 
Hold a dollar bill at the tailpipe while it is idling. See if it gets sucked up just a little as it idles. This will tell you if you have a burnt/ poor sealing exhaust valve (which is very, very common on that model.

Is the connector end of the cam sensor pointing back toward the firewall, parallel to the block? If not, I bet your cam sensor isn't "synced" properly. You don't set timing on those, you set the sync signal between the cam and crank position sensors. There is no way to set this without a good scan tool.

Also, wiggle the injector connectors at idle. There is a pretty severe bend in the harness where the wires enter the connector on 00-04 4.0s. I have seen broken wire strands many times too.

Check these "freebies" and report back.
 
the dollar bill trick worked. it idled fine on start up but then started to sputter after warming up a bit. the dollar sucked up to the tail pipe like you said. now i gotta call clearwater and see what they want to so bc this was a brand new head. thanks to jody and the others that chimed in. also i tried the "wiggle" test before posting with no result, and the cam sensor looks to be in the correct position based on reading some of jody's other posts.
 
i agree with everything said but i still think synchronizing that cam sensor would be a first route before jumping to conclusions about a bad head. like jody says, those have to be syncd with special scanner and ive had a few that i dropped in somehow perfect and didn't need to but I've had more that i had to send off to have syncd too so.
 
i know for me, ive had some real rough running wjs with that issue from the cam sensor very similar to his and it has always been that sensor not right. and I've never come across a bad jeep head as far as valves go: cracks yes, pistons and skirts too, but in my long time with the 4.0, never seen one with bad valves but i'm forgetting this head isn't factory but rather new company new so i guess they are to blame here afterall!
 
88jeepster said:
i know for me, ive had some real rough running wjs with that issue from the cam sensor very similar to his and it has always been that sensor not right. and I've never come across a bad jeep head as far as valves go: cracks yes, pistons and skirts too, but in my long time with the 4.0, never seen one with bad valves but i'm forgetting this head isn't factory but rather new company new so i guess they are to blame here afterall!
Click to expand...
I've seen 3 or 4 this year with valve issues!
 
so to update this thread, I have done much testing and finally found a solution. the dollar trick scared me into thinking there was a problem with the new head. so I called on a few buddies with more tools and knowledge than me. I used a snap on scanner to look at the cam and crank signals, all checked out ok. there was no check engine light on or pending codes. the next step was a cylinder leak down test and compression test. both tests returned normal consistent results, so not a faulty valve-AWESOME! but now what? I borrowed some sensors from my sisters wj, eventually got to the coil rail and bam!-ran great. thanks to all the help along the way.
special shout out to mark and chris at sanders automotive in Pittsboro, nc for the use of their time , tools and knowledge.
 
sorry to hijack this thread, but i have a 2000 wrangler having the exact same issue i replaced all the sensors and it randomly runs like crap. I might have to try a new coil rail as well.
 
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