• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

intermitten missfire

94XJ2door5speed

NAXJA Forum User
Location
Norwich, CT
I have a 94' XJ with the 4.0 and 5 speed manual, i have replacer the cap, rotors, plugs, wires, crank sensor, and cam sensor and yet still there is a whole engine missfire across all cylinders between 1800 and 2300 rpm, i tested my tps and it is out of spec but not enough to affect the computer, anyone else have the same problem or any ideas my friend has a 93' auto with the same problem and she replaced the distributor as well no such luck. I'm lost and out of ideas.
 
I haven't had that problem with an XJ yet, but the same generation PCM in other manufacturers vehicles can have an intermittent O2 lean condition, that doesn't trip a MIL code, but on some vehicles may be an intermittent check engine light. There may be a code 51, there may not. The check engine light may illuminate for just a second going up an on ramp (low vacuum) at a round 2200 RPM and/or cruising in the same RPM range.
I don't really know if this is possible with the XJ, but is common in other makes with basically the same PCM.

A fuel pressure/volume test may also be helpful, a lean motor typically acts up at or around 2000 RPM and then again at high RPMs above 3500 ( you often loose some top end).
 
Last edited:
this does make sense and doesnt, i used my friends computer and got the same problem when his didnt do it, but when i pulled the bosch plat2 the other day they were white which normally means lean tan is good if i recall correctly i know the pressure regulator vacuum hose boot was bad but replaced it and it didnt help, honestly it didnt do it before i changed everything, when i got it it had 193,000 miles with all stock parts i did the usual tune up and thats when the crank sensor died so i replaced it problem solved, thats when the skip started. So we put the cam sensor on the o-scope and it tested bad when i replaced it it made it better but it didnt fix it, the skip used to be 1500-2500 so the cam sensor just narrowed it down. i have also been told the distributor could be worn so it spins more in an eliptical pattern than a perfect circle. Back to the tune up, the stock fuel filter was still there and the stuff that came out of it was more like motor oil than gas, could the filter need to be changed again only put 1,000 miles on it since i got it a month ago? The guy who did this with me was a GM, FORD, and now a NISSAN tech but he has driven nothing but XJ's since he was 13 and he is now stumped all his fancy stuff couldnt tell him either.
 
Back
Top