I have a 98 Cherokee with the 4.0. About a week ago it starting missing pretty bad while idling, so far I have replaced all the spark plugs the distributor cap and rotor and set the timing. None of this helped, next I was thinking of replacing the injectors but still not sure. It's throwing a code saying it's running too lean, and my exhaust is a dark gray under throttle. Does anyone have any ideas?

 

check the fuel pressure

 

Might be your O2 sensors. I think your 98 has 2 of them.

 

Dang Thieves will steal anything but a whole engine is ballsy.....lol


just a little levity


O2 sensors maybe

 

I was having the same issue on my '98, replaced both upstream and down stream O2 sensors and rough idle gone. I used NTK brand sensors over the cheaper Bosch. I also took the time to clean up my grounds. under ECM, near neg on battery cable and back firewall. I dont know if related, but I had replaced my clockspring and still had airbag light on. after cleaning the grounds, light is off for the first time in a year.

 

CORRECTION! Computer said lean in bank 1, first I will swap out #1 injector with #2 and see if this changes anything

 

Another vote for o2 sensor. You only have one "bank" in that Inline 6.