Ok my 99 xj 4.0 gets a rough idle and will not run but only when it is under heavy load or gets up to full temp and running the AC. I'm in Florida and AC is a must have. I did a tune up (plugs, wires, cap and roter) just a few weeks ago. Befor that I relaced the fuel pump (because of this problem) thinking it may not be getting the fuel pressure it needed and it was better for a few weeks but the issue returned. When I got the jeep a year ago I gave $900 for it because it would just stop running and leave the owner stranded. At that time I put a Crank Position Sensor and Throttle Postion Sensor in and it ran like a top for 4 or 5 months but now this problem is killin me. Could it be that the TPS or the CPS need replacing again? Can I test them? It does not throw a code that I see like it had when I got it. Any ideas would help I am going crazy trying to figure this out . Please help!!!