Went to drive my 92 4.0 to class this morning. It had a pretty hard start, then from there drove fine until I reached a stop light, where it started sputtering/idling rough. When I started moving again it was fine. Another light, more sputtering/idling rough. Got to campus, decided I would try re-cranking it to see what happened. It had a VERY hard start and was sputtering and idling VERY rough, then it stalled. I went though this process about 6 or 7 more times before it was driveable, although the RPMs did not drop below 1250, even in park. Once I got going a little bit everything seemed fine, no issues at stops or anything, except the high RPM. I did the on/off/on/off/on trick and got no codes. Tried cranking it again when I got home, cranked normal, still high RPM though.

Help?

 

when that happened to me it was a busted vacuum line coming from the TB id check those.

 

You wouldn't happen to have a good picture of what I'm looking for would you? I'm a newb when it comes to engines. Learning very slowly.

 

Just drove it again. Aside from high RPM no issues. I nearly put the pedal down, no issues. Idk why it was acting up so bad earlier. I hadn't driven it all weekend. Could that be it?

 

No picture but ill try and explain. While looking at the throttle body from a front view you got 2 vacuum hoses on the left side of the TB. One leads to the map sensor and if that one is busted your jeep will run like its out of time and even die when reaching stops. Just follow your hoses and play round with it plug anything that seems out of place. The map sensor is located behind the engine where all your wires are running under a steel plate. Just google map sensor for an xj youll find pics of it.

 

Your throttle position sensor may need adjusting as well or you got something else thats starting to fail which is not uncommon for an xj that age.

 

I checked all the hoses and everything, didn't see anything that caught my eye. It seems to be running fine again. Ill look into adjusting the TPS for the high idle RPM. Thank you so much for the help.

 

Might be a good idea to pull the throttle body and give it a good cleaning along with your idle air control valve (which is a sensor attached to the throttle body)

 

ive tried everything i could think of and i'm posting on this because your problem sounds kinda like mine. Usually mine will stall when i'm ideling or at a red light sometimes itll even do it going full speed down the road. Along with this sometimes it is hard to get started but i can wiggle the wires going to the pcm i've been getting i primary ignition coil code but i've replaced everything ignition wise. ive replaced wires, plugs, coil, distributor cap and rotar button. If anyone has any suggestions before i go and spend all this money one a new pcm please let me know something.