I have a 00 xj 4.0/ AW4 with 115k on it. Bought it in 2013 with 99k. Previous owner dealt with and replaced the notorious cracked head, which I was given a heads up to inquire about before purchase. The only part I had to replace up til now was the TPS, which threw a code, and was fine after replacement. I've grown quite attached to this Jeep, it's been good to me, and up til now, it's been a peppy little thing.....
Fast forward to about a month ago...I was driving, and it would randomly buck/hesitate, like it wanted to stall while in motion...since then, it has done it again, I notice that it happens: after I've been driving for awhile, and engine is to temp, and while Im in 4th gear, with my foot on the gas. I had it plugged in to a scanner but no codes came up...
Since this started, I notice it bogs down bad going up hills, and the idle seems rough.
Earlier this week, when it did it's hesitation /stumble, the check engine and check gauge lights flashed and went back off...was this a "soft" code that I can recheck? That same day, it also stalled twice, and cranked a little hard to start. This was the last time I drove it, out of fear it would stall and I would not get it restarted in traffic...
I am a girl Yes, but I was raised around cars and trucks my whole life, so I like think that I have more automotive sense than a typical woman, but Im used to carbureted classics. This is my first vehicle with real electronics...and boy am I learning!
Since this issue started, I had battery tested, which I was was told was shorted, so I replaced it, along with terminals, which were corroded. I also had alternator tested, which passed with flying colors. Even with these checked and replaced, the issue persists, and actually got worse in my opinion...
My gut is telling me this is an ignition issue...but could it be as simple as a loose/bad ground? Where should I start? I really like owning a Jeep, and I don't want to give up on this beast, I appreciate any help and guidance! Thanks guys!

 

Use a scanner or code reader that can find "Pending Codes". Sometimes a code will come and go but be stored as a pending code.


"Since this started, I notice it bogs down bad going up hills, and the idle seems rough." It's possible you have a Catalytic Converter plugged.


Is this your exhaust system?

 

I would look to the fuel pump, try to check your fuel pressure. Fuel pump problems can be cutting out, stalling, low power, hard warm starts... Its also possible that if you used an aftermarket TPS that it isn't returning the right values. Dealer sensors are the best. The are other possibilities like the cam or crank sensors but crank sensors don't usually cause bogging down, they usually cause hot stalls.

 

This. You absolutely positively need to know what this code is.

Post the EXACT code here for comment.

 

I just had this same type of problem but it was accompanied by a crazy loud grinding sound. It ended up being my alternator. It worked fine as far as recharging but the bearings went bad and when it wouldn't turn properly it wouldn't give enough power to the battery and it would stall or sputter, but when it did turn it worked perfect. If their suggestions don't work try checking to make sure the alternator spins well.

 

Update:
Since posting this, in the last week, I enlisted the help of a buddy and we pressure tested the cat...came back A-ok. We tested fuel pressure...A-ok. I had it ran again for codes...nada. Since OP, it now is consistently shutting off while driving (again, it's always when it's up to temp). Always cranks and refires though. Rechecked relays and ignition...all check out.
Somebody told me that it has to be the cps. (crank or cam? Do xjs have both or one or the other?) That these suckers when shot, can check out fine when cold, but when they get hot, they can cause intermittent failure and NOT throw a code...does this make any sense? I thought when the cps goes out, they go out all together, not just when they darn Well feel like it?
Since I explored all these other options, should I put a sensor in? Is it worth the labor/expense to change it and hope that's the culprit?
I Thank all of you guys who gave me input so far, it's helped me narrow the list of suspects. I will keep y'all updated!

 

Final Update:
I've been busy, but I wanted to confirm...It was the CPS.All symptoms gone, and my xj is full of giddyup again! I can enjoy driving again!
Now I can continue looking at suspension upgrades...
Thanks to all!

 

good job!!