Swim

sometimes stumbles on accel ... nuetral shut down restart then runs fine...

BlueRidgeMark

Any codes? Not much to go on, but I'd be looking at the 02 sensors. A look at your fuel trims would help. Got a Bluetooth OBDII reader?

Vacuum leak is another possibility.

Swim

No, dont have one, took it to autozone for free read. Said P0138 and O2 circuit signal had high voltage Bank 1, Sensor 2. But they were confused as to which O2 sensor to order...and want to learn more before buying any O2.

emx72

p0138 the sensor after the catalytic converter , make sure to only to buy NTK 23099 (not bosch sensor). BUT BEFORE you but go underneath the Jeep and trace the wires. Many times the clip that holds the wiring to the sensor falls off and the wires fall on the drive shaft which wears them out and basically cuts them causing your code (which was the case in my Jeep). Do NOT buy this from autozone they charge $77 vs $30 shipped from Rockauto.com (plus you can take off 5%, get a coupon at retailmenot). But first check your wiring under the Jeep to see if it's worn out.
Also, the oxygen sensor after the catalytic converter would NOT cause any issues of the Jeep running rough it is strictly for emmsions. The sensor before the catalyctic converter would cause issues but it would not give the P0138 code.

Swim

All four wires ripped apart by shaft, looks to be brand new cat and sensor ... clip is fine, mech prob didnt get it on there good.
four wires 2 white 1 blue 1 gray could not tell if whites were specific, just went by clock order. Still runs same as you said it would. Will get codes checked to see if its changed. Engine light still on also...And if the Sensor does not affect engine management I can toss the cat and sensor, correct? Whats your guess on the cause of stumble during warmup at about halfway to full temp. Thanks.

lawsoncl

Yeah, the two white wires are usually for the heater in the O2 and doesn't matter if swapped. Why ditch a perfectly good cat and rear sensor though? My thought is the upstream sensor is bad, not heating up quick enough.

BlueRidgeMark

That's true of the earlier XJs, but it's NOT true of the later ones. The fun thing is, I'm not sure what year it changes over. It's either 99 or 2000. On the 2000 & 2001 for sure, and possibly the 99 (& maybe the 98), the rear sensor very definitely IS part of the engine management system, NOT just for emissions.

Since he's having running problems, and the rear sensor is setting a code, I think he'd be wise to replace it. (I''m assuming he's fixed the ring problems at this point.)

Swim

ok gonna check codes with rewired 2nd.
and is it ok to try and run it with the 1st O2 sensor unplugged or is that unwise? any suggestions on good sensor brands to go another 166k. looks like might haveto do both, could some other sensor be the culprit also? ill get back with code chk...

BlueRidgeMark

Sensors on these beasts are pretty touchy. THey like Mopar (NGK/NTK) Aftermarket not recommended usually. That said, I've been okay with NAPA on the O2 sensor. Seems to not be as picky.on those.

Swim

could this be the cause seems like a very broad trouble code, what kicks this code in to action?

Have to say I already have carb conversions and 4 barrel v8 day dreams rolling around in my head...

​​​​​Thanks for all advice you guys know thdese well.