I have a 99 Wrangler Sahara 6-cyl manual that I got about a month and a half ago, my first Jeep.
I noticed that if I don't run it for about 4-5 minutes before heading out, at some point early on in the trip it will start cutting out, it bucks for a bit then it's fine and it won't do it again during that trip. If I do warm it up it seems to be fine.
I also have a problem where, if I let it idle for too long it will start to die out, increase the rpm's, die out, increase, etc, etc. Sometimes it dies altogether, others, after I blip the throttle, it smooths out.
I've also had the resting idle sometimes go to 1500 - 2000 for a couple of minutes, then it will drop back to its regular 800 or so.
I've had the CEL come on 2x. First time I had P0121, P0123, and P0135 codes. I cleared them and about 2 weeks later got another CEL with only the P0123 this time.
I've replaced all the plugs, plug wires, cap, rotor, and ran a couple of tanks of fuel thru with injector/fuel system cleaner without any change in the problem.
Any suggestions?? After reading some of the forums, I'm inclined to look towards the TPS and cleaning the throttle body, and maybe check the O2 sensors.