Ok so i noticed an issue with my RPMs today, note: auto trans. It idles normally at 750 but and times in P it will jump to 1k then back down to 750 and repeats. when i shift from P to R it jumps to 1.2-1.5k rpms then goes back to normal. when shifting from D to N it almost stalls and when going from R to P it almost stalls. now ive already checked for a vacuum leak using gum cutter, none of the vacuum lines or gaskets showed any increase in rpms when i sprayed them with the gum cutter. its a 99 xj sport, anyone have any suggestions on what to check?

 

Clean your throttle body and IAC,

http://cruiser54.com/?p=60

 

i just cleaned them about 2-3 weeks ago but ill clean them again just incase

 

Didn't you have a possible fuel injector issue? Have you resolved that yet? These may be related runnability issues..

 

yes i still have that fuel injector issue, now that u mention it, it kinda makes sense

 

so it just shut off on me going from R to N, i think its the crankshaft position sensor. coworker who has a 94 zj had the same issue and that was his issue

 

It's not the CKP.

Do you have access to an OBD-II scanner? Check what the MAP, TPS, ECT, and IAT values are at cold startup. Chances are one of those sensors are telling the PCM to dump extra fuel. Could even be the O2 sensor...