Trouble please help
So I have an 04 jeep cherokee SE 4.0L.. I've had it a little over a year now. My car was sputtering when coming out of an idle (occasionally) and cutting off when sitting in idle after getting up to temp. When it sputtered the rpms would drop below a thousand, but if I kept hitting the gas it would correct itself. This only happened coming out of an idle, while moving it was fine. Over time it became harder and harder to start after these kills. I went ahead and got the throttle body cleaned(after many other attempts at fixing it) and the problem stopped.About 2 weeks later while driving it began to misfire, or "break down" as my mechanic told me, so hard that it would jut the car forward while braked. The code P0442 was the code which is an emissions/misfire code is no help at all. I had my mechanic replace the cpu, ignition coil, and wires ( not sure which wires as I am not too good with cars) but he's saying that it has to be a short somewhere which is not good news. Have any of you had this problem before or have tips on figuring it out? I have an appointment with the dealership soon and I want to go in prepared. Thanks!