Missing Cylinder 97 Jeep 4.0

[Halftrac]

I'm working on a 97 XJ with 4.0 with a missing cylinder. Computer says number 3 sometimes others. Changed plug,wires,cap,rotor. Swapped out injectors with a running 4.0. Still has a miss. Could it be crank sensor? Grounds look good. Can clear code and get it run on all 6 but under an hour back with a miss. 170,000 miles compression is good.

 

[C.Berry]

Might just need new dizzy...? Honestly the computers on that year 4.0 are PITA i have missing problems also take to dodge dealer and tell em you have a miss and you think its from one of the 4830409384 recalls they had. well for my Grand Cherokee it was recalled a bunch good luck fill us in if ya figure it out!!!

 

[Baker]

How are the o2 sensors ? I had a dodge that did the same prob and I went through everything turned uot to be as simple as an o2 sensor

 

[transman731]

probably a carbon issue

 

[dkrajcovic]

burnt valve ????

 

[Halftrac]

Figure a burnt valve would show up on a compression test.?

 

[transman731]

they are a carbon prone engine, i have seen carbon stuck valves in them many times. my guess would be small pieces of carbon freeing up and hanging in the valve seat.
anything is just a guess without seeing what's actually going on.