I got a 95 Jeep Cherokee XJ 4.0 h.o.new cylinder head. And I crank it in the morning it has a kind of up and down idle. It will idle up then it will act like it's going to die all of the sudden kick in and start running smoothly again. I will let it warm up then I get going down the road and it starts backfiring theough the throttle body until I let off the gas and barely push the throttle. If I give it more than a quarter of pedal it will start spitting and sputtering again. It will eventually clear up and quit doing that and run fairly smoothly. But if I drive it for a while then cut it off go to crank it again it doesn't want to crank unless I push the gas halfway to the floor then it will crank up.. if I let it sit too long it will start loading up and act like it's fouling a spark plug. Do y'all think it could be one of my sensors like a map sensor or idle air control or Tps...any help

 

You know what to do bro. Check all that ****, something ain't happy🧐

 

Check the vacuum lines. May have bumped one just enough to split it. A pinhole is all it takes. Remove and clean the IAC and throttle body. Dont operate the IAC by hand if you do clean it. You said it acts as if the plugs are fouled. Check them and see. All of them. I would also check the fuel pressure, just because. Find, remove and clean any engine grounds. Im not sure where they all are for a 95 tho.

Thats where i would start if it were mine. Simple stuff.

 

thanks for the advice...I cleaned the throttle body and iac it did nothin. I think I'm just gonna replace all the sensors since they never have been...I looked on eBay and all the sensors are like 50 bucks cheaper than autozone and other places plus they are the right ones cause I checked part numbers...all vacuum hoses are good and engine grounds are tight...also gonna put some non foulers on the plugs cause ive had trouble with number 3 and 4 cylinder fouling plugs even before I put a new head on it.....rings and compression are good though