Bought a 2001 Jeep Cherokee for my daughter. It now has a problem that has received a bit of attention on this forum. No CE light - just runs rough after warm up. throws codes P0300, P0301, P0306 - misfire codes for 1 and 6. Replaced plugs, coil rail, cam sensor, altenator, battery . . . Where to go next TPS or Crank sensor or ECM? Had it to several garages but they didn't fix anything. Runs great till it warms up and I let off the throttle then it starts the misfire until I shut it off and start it again. It will then run okay for a bit then starts the misfire again.
One of the members on here reported a same problem, and he had to rework all the valves. Did you already try a seafoam treatment via the brake booster vacuum line? Sometimes misfires are caused by too slow closing valves, due to carbon buildup on the valve stems.
Greetings Nev
Looks like you've replaced many parts but still no 'fix'? I like Frank's idea but a low cost, easy to replace item is that Crank Position Sensor and when they fail, it can be progressive or 'all at once' and no start / run possible unless replaced. I have the 4.7 ( you have the 4.0-wasn't sure?) and the mounting tab (takes single bolt to block) of the CPS cracked at the body ( all plastic) and let go and it was floating in its aperture although it never came out-the seal was all that held it in place. Until I figured out what was up, it ran terribly- like you are describing. A buddy back in Houston just bought one for his GC at Auto Zone for about $15. Good luck and let us know how you go? ATB!
Thanks for all the thoughts and advice. After replacing every electrical component and having the vacuum system checked for leaks, I have concluded it must be mechanical (valves not closing properly). If anyone wants a nice jeep Cherokee for $1500 that probably needs a valve job let me know!!! Otherwise I think I'll try to do it myself - don't really have the time though!!!