Need Help! Stumped.
I have a 93 jeep grand cherokee with the 4.0. The jeep for the most part drives great when it is running. I have noticed it does have a rough idle when stopped and transmission is in drive. If the jeep is put in park or is in motion their seems to be no problem.
But if i leave the jeep parked overnight with out driving it for 5 or more hours it will run very rough, spit sputter, and seems to be a backfire in exhaust if i try to give it gas. I have to wait till the jeep is at operating temp. so it can be drivin. I can then usually drive the jeep all day with no problems. I'm hopeing somone may have had this problem and knows how to fix it.
I HAVE CHANGED the fallowing: Fuel pump, Fuel filter, Idle air control valve, MAP sensor, Air/Temp flow sensor, coolant temp sensor, oxygen sensor, Plugs twice ( they seem to run a little hot), plug wires, cap, rotor, igniton coil. brand new battery. All the vacuum lines look good, canister not cracked.
I thought to change the TPS but i get NO codes at all, and the sensor tests good with the volt meter, with throttle shut and open.
Its not a security issue, the alarm is disarmed. Also the PCM has been changed before i owned the jeep, its not a factory PCM which leads me to think thet the previous owner has changed it.
What would make the jeep spit and and almost die out after sitting overnight? could mostiure be getting somwhere? i have no idea what to check next. it seems to me if it was anything electrical i would be getting a code. And i am not getting any codes what so ever. Please help if any ides.
if it is a fuel presure regulator, wouldnt the jeep run bad the whole time?