Wants to Stall/No CEL

Ok so a few weeks ago I was pulling out and got up to about 15mph and my car backfired through the intake for a second or so and acted like it wanted to stall....gave it some gas and it finally caught up with itself and was good to go...then one day my CEL came on..had the code scanned and it was both 02 sensor throwing a code....had it looked at and said that my upstream 02 sensor wasn't inside the pipe far enough so it wasn't getting a good reading...(I had had my entire exhaust done a week prior) so they welded me up a slimmer bung and everything was fine for about a week....which was Sunday night coming home from a concert....started it up and my CEL came on...this time code P0137 (low voltage to 02 sensor Bank 1 sensor 2) Bought a downstream 02 sensor at napa this morning, had my buddy put it on for me, old wires off old sensor were frayed and twisted.....ok so started my jeep up...no light and the jeep felt great...no sluggish feeling at all....get up to the light and take off and it did it again...acted like it was stalling out....pretty much like when you mess with the TB and have to floor the pedal to keep the rpms up....thats what it feels like....I just can't keep throwing money at it hoping I am going to fix it....I know that you can't clean the tps, but I don't want to spend $50 on a new one if that isn't the problem....

upstream 02 sensor was also checked out and no problem with it...

any ideas?

Can't hurt to pull the TB off and clean it real well. Pull all the sensors out before cleaning it, and don't clean the TPS or the MAP sensors. You can clean the idle air control (I have to clean mine on a regular basis or I get some weird idles as well).

My initial thought is the TPS isn't working, but there's not really a way to test that like on the older models.

Is it still trying to backfire through the intake, or did that clear up with the work you had done?

It will only backfire through the intake if I try and punch the gas while its stumbling. Im getting ready to go out there and check the TB and clean the IAC. Might unplug the TPS just for the hell of it and reconnect it....its really starting to piss me off because I hate not being able to drive my jeep normally. I am wondering if I should just bite the bullet and buy a new TPS...someone mentioned to me that if could be a crack in the manifold? I just don't think it would clear up for a week and then act up again.....

A crack in the manifold could throw the upstream o2 sensor off, as it would be seeing more oxygen than normal and therefore dumping more fuel to compensate. That would mean you'd be running richer than normal, but you're getting backfiring through the intake, which indicates the opposite...a lean mixture.

Another thought, coolant temp sensor. I've seen (and experienced) where it goes bad and basically lies to the computer saying it's warmer or cooler than it really is, which again would screw with the fuel mixture. If i'm not mistaken there's a way to test it, but I can't remember off the top of my head. I'll run out and look through my FSM in a bit and see what I can dig up.

Now that I think about it some more, have you tested the upstream o2 sensor, or replaced it recently? I see where you had a new bung welded in, but was the sensor replaced at all?

sensor was fine and so was the wiring. the last code it threw was for the downstream sensor which was replaced today. not throwing the code but still acting weird. I just went outside and removed the IAC and cleaned it up...it was black and nasty looking...also cleaned the TB.

Also I checked the fuse for the heater circuit for the O2 and it was blown. (again) this is the 3rd fuse in a week that I have replaced....now I am sure that the fuse was blown before the 02 sensor was replaced today, so I just replaced it and I am gonna see how it does tomorrow and re check the fuse....its just embarrassing...I'll be driving along and then all of a sudden my jeep as no power and is stumbling to keep up and people behind probably think I'm slow.

O2 sensors don't always throw a CEL, so the upstream still may be not functioning properly.

3rd time this week that fuse has blown? Wonder what else is on that circuit...

Well I drove it to work this morning...started it up and it seems to run a bit better. didn't have any hesitation or stumbling...although I only have about a one mile commute to work....so we will see how this afternoon goes...i'll take a long way home and see what happens.

But I am just wondering what causes the heater circuit fuse to keep blowing? unless it is just that upstream 02 sensor causing all the problems....

felt good coming home....no hesitation/stumbling.
Still feels like the idle is a little out of whack.....will continue to monitor everything.

Check your cap and rotor. First you may have carbon build up in cap and while you have it off check for grooves worn into your cap contacts from the rotor. After approx 100,000 to 130,000 miles the bushings in the distributor wear out and cause the distributor shaft to wobble which causes the rotor to hit the contacts of your cap. More importantly, on the HO models with the cam positioning sensor located inside and triggered off the dist shaft. You will get a cam sensor error and stalling at random. The motor will misfire and cause the ECM to go into limp home mode. The sloppy distributor problem throws most jeep owners for a loop and confuses even the best of jeep technicians. I have made lots of money purchasing jeep xj , yj and zjs with the 4.0 motor that need distributor replacements and run like new when replaced. Always replace the cam positioning sensor when you replace the distributor. Most people start Easter egging sensors and can't figure it out.

Well, funny story...I was cleaning my jeep out last night and I found a brand new unopened Distributor cap and rotor that was never installed, so that is what I will be doing this afternoon...I don't know why, but I did a tune up about 4-5 months ago and I never changed the cap and rotor for some reason.....but I did the plugs and wires...

Ill change that and see how it goes....