2000 jeep tj misfire

SPC.BELL13

Active Member
Joined
Sep 7, 2010
Location
dever NC
i keep getting misfires... i have had the valve springs rotated, compression tests, cps sensor changed.... all kinds of stuff. i am looking for someone who has had a similar problem and has fixed it. also it will misfire when i drive it for a while on the highway and then turn it off. If i start it back up while motor is still hot it will misfire.

Please any suggestions?
 
Start it up, while its running hold a dollar bill at the tailpipe. If it has a burnt/not sealing valve, the bill will actually suck up into the tailpipe when that cylinder fires. I use this trick all the time.

Im doing a 4.0 valve job at work now and diagnosed it this way.
 
well guys i appreciate it that info. Im gonna start with the injectors and go from there if there are any more suggestions please keep the posts coming.

thanks you all.
 
Love the dollar bill trick!

First what type of spark plugs did you use? Has the coil ever been replaced? CPS (cam or crank) may want to look into replacing the other.. '00 4.0 you probably over 100k miles its time for all the little stuff to start to need replacing.
 
if you have Bosch plugs then id change them back to oem. i use autolite platnum and it works great. If it were one of the sensors then it wouldnt cause a misfire after its already been running. If it were valves then it would misfire constantly.on those year 4.0's there was a issue with the #3 injector getting too hot and causing a misfire. there is a TSB on this website and a fix using a insulator sleeve. this should fix your issue.

http://www.cherokeeforum.com/f2/01-xj-misfire-cylinder-3-a-42281/
 
hey guys im back

i have gotten the valve springs tested... and compression tested, all checked out but im still getting a multiple cylinder misfire. I have replaced coil pack, injectors, plugs, down stream O2 sensor, CPS (crank positioning sensor)... I was told by the dealer that since it is an after market coil pack it could cause the misfire. it had an after market one on there before the problem started and it had no problems... funny thing is when i installed the new coil pack rail the check engine light went off but then came right back on the next day and when it comes on it flashes so i drop the speed and it stops...


ANy help is appreciated.

Thanks,
SGT. BELL
 
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