96 Jeep 4.0L Cherokee Multiple Cylinder Misfire

I have had this problem for a few months that started out with acceleration stalling and check engine light yielding codes with cylinder 3,4, and 5 misfire. I replaced the Crank Shaft Positioning Sensor and the It stopped stalling but check engine light came back on after a few weeks with Multiple cylinder misfire. I replaced the spark plugs and wires and the check engine light went off for 3-4 days and then came on again while down-shifting up a slight hill. The jeep does not run bad at all and does not miss in performance or sound. I noticed a decent crack in the exhaust manifold and replaced it. The light went off for 3 days and then was back on while driving up slight hill. The exhaust smells slightly rich. I have replaced Fuel filter, plugs and wires, Throttle positioning sensor, and am about to do cap and rotor although now the codes have progressed to cylinders 1- 6 and I dont think its those. I have read in other threads where it is suggested that carbon build up on valves can cause this problem. I tried some combustion chamber cleaner with still no success. What are my options? Take it to dealer? Replace something else? Please help? Thank you in advance for reading my post and for any hint of help.

Jim

No to dealer. You can do it just as good. Just as a baseline check, how about checking the compression? It will help tell you about carbon build up on the valves too.

x2 on cap and rotor.

Double check all plug/coil wires are securely attached on both ends.

Check ground wiring at back of head and battery grounds and engine grounds and the one near PCM on left fender. Weak grounds can really cause strange things.

Clean Battery terminals. (With the batt terminals OFF of the battery, hold them together 30 seconds. This will reset PCM for fresh start on adjusting to the new parts which might help.)

Good Luck,
Orange

I was getting those codes, but it was running like crap. I had replaced my fuel injectors with the Bosch style and the electrical connectors weren't making good contact. I had to replace them with connectors off a new model XJ.

Thank you all. I am going to change the cap, and rotor and see what happens.

Check your fuelpressure. Low pressure will throw all kinds of codes and will have you chasing your tail and scratching your head.