2003 TJ w/4.0. I've been troubleshooting my way through a recent history of misfires w/CEL..."fixed" with new Cam/Crank sensors because it did improve running and the CEL hasn't come back. The engine starts immediately. It seems to be down on power and runs rougher than usual. Occasional backfire through the intake...hard accelleration stutters at first but sometimes clears and hits strong. On occasion, once the engine is at full temp for a while it starts running perfectly....something that makes me think it may be a coil or injector reacting to getting hot enough.
What I have done:
New crank and cam position sensors, set the cam sync and monitored to prove they are sending good signals.
Checked fuel pressure...it is steady and within spec.
New APP985 plugs...plug #2 looked like it had a cracked insulator or maybe was burned a bit. The rest looked worn but fine.
Smoke tested the vacuum system, found and fixed a pinhole leak or two.
IDed that there is a vacuum leak around the throttle plate shaft and will be fixing that but I don't think that's the source of the main problem since it "can" run perfectly for spells and that is upstream of the sensors.
Did monitor for misfires and since swapping the cam/crank sensors there hasn't been a single one in the history log.
Monitoring O2 sensors "seems" to indicate a lean condition and it keeps compensating up and down in what seems to be in sync with the engine stumbling.
So, at this point, I'm thinking it's down to the coil bar or an injector...thoughts before I continue w/the parts cannon?
What I have done:
New crank and cam position sensors, set the cam sync and monitored to prove they are sending good signals.
Checked fuel pressure...it is steady and within spec.
New APP985 plugs...plug #2 looked like it had a cracked insulator or maybe was burned a bit. The rest looked worn but fine.
Smoke tested the vacuum system, found and fixed a pinhole leak or two.
IDed that there is a vacuum leak around the throttle plate shaft and will be fixing that but I don't think that's the source of the main problem since it "can" run perfectly for spells and that is upstream of the sensors.
Did monitor for misfires and since swapping the cam/crank sensors there hasn't been a single one in the history log.
Monitoring O2 sensors "seems" to indicate a lean condition and it keeps compensating up and down in what seems to be in sync with the engine stumbling.
So, at this point, I'm thinking it's down to the coil bar or an injector...thoughts before I continue w/the parts cannon?
