random sputter/ backfire
 

my 98 xj started this the other day out of the blue. started having a random stutter with a backfire at low rpm's as i am accelerating from a stop. it seems to do it more while going around corners.

i did find a bit of melted wire on the harness going to the upstream o2 sensor. a few inches past the fuel rail, and touching the number 1 exhaust pipe. i re taped up the wire and zip tied it out of the way. i didnt look to see which wire had melted, but it was down to bare copper and grounding out.

tonight i replaced new dist. cap, button, and wires. they were only 2 years old, but were autozone specials. so i didnt mind tossing those on. no improvement.

at this point i am not sure what to do. did grounding out the o2 kill it? i have no codes stored or pending. and i dont want to start throwing parts at it. both o2 sensors are less than 2 years old and NTK brand. all the sensors on the throttle body were cleaned when i installed my bored tb. is one of them acting up?

i am not opposed to trying a new coil, as the one in it is probably the original with 254k miles on it.

recently one of my injector orings went out, and i replaced all 12. running ford yellow injectors, that i bought from the forum as cleaned and rebuilt. the hesitation started a week after having the fuel rail apart.
any other suggestions?

bump it up

You said you c/o the cap, rotor and wires how about the plugs?

Yes plugs are only a few months old. Standard Ngk, nothing fancy.

on the way to work yesterday i had 0 issues, but on the way home it did it 3 or 4 times in a 25 mile each way trip. lasting only a few seconds each. if you let off the gas and slowly throttle up it goes away.

i did go ahead and order a new omix coil, i figured for $35 shipped. no reason not to try it. and i get to clean off the sensor grounds when i bolt the new one up.

any other ideas? i hear the crank sensor can cause these issues. if i test the crank sensor will it show an intermittent malfunction? or do i need to be testing it while i am getting the studder and minor backfiring?

really stumped at this point.