Hey guys,

first time posting, but I've been cruising the forum for a while. I'm having an issue with my heep. I'm getting backfires, bucking and rough idle. I've replaced the crank sensor, tps and map sensor and the problem still exists. The only occurs when the engine is warming up or just started. Once the PCM is in closed loop it never seems to be an issue. I have sprayed some TB cleaner through the IAC, but haven't actually pulled it off to clean it. What would anyone recommend be the next step??

 

Forgot to mention. No codes are present.

 

Is it back firing through the intake?

 

yes

 

Pull off the throttle body and clean thoroughly. Clean your injectors, too. Might help a bit. Clean the vacuum fittings and the sensor on your intake manifold, too. I've done all this and it smoothed out the idle a bit.

 

Oh, missed the backfiring thingy. I forgot what's open loop/closed loop at warm-up. Got a factory service manual?

 

I don't have a FSM. PCM is in open loop on start up. After warm up it operates in Closed loop. feel free to correct me if I'm wrong.

 

Also forgot to mention I put on this aftermarket ignition kit: http://www.performancedistributors.com/jeep4.0.htm

Problem existed before the ignition kit was installed. Could the distributor itself be the culprit?

 

You could try just swapping with a cheap distributor and see if it helps. Get a refund if it doesn't help lol. I'll pm you the link for an fsm soon.

 

Forgot to mention...it happens the most under load, if it starts bucking I can push the clutch in and rev it to the moon just fine. So I don't think its a fuel pressure issue...any other thoughts?