Check your rear cable harness. My `97 had those symptoms, replaced the O2, had a Jeep mechanic put a 4oz can ??? that was $10, etc, etc. If the harness touches the engine anywhere it will rub through the wires and short the injectors yielding a misfire. Search my threads for a photo.

Like you that misfire was my first post here. Luck to you.

 

Heh. Told ya!

 

Good stuff! I have family in E-town. Rep KY lol.

 

P0171 is persistent.. CEL claims the fuel mix is lean but it's actually running hella rich.

Fixed the vacuum leak on the rear CCV line by "splicing" in a large hose. No change. Moved all of the wiring around and have replaced or moved all fuses and relays.

I can't hear any (extra) noise from the engine compartment to assume it's a cracked exhaust manifold. Gasket could be letting outside air in maybe?

I've got the battery unplugged to drain the system before spraying electric cleaner on every connection I can find.. new MAP comes in Wednesday hopefully. Jeez.. I just want this thing running right so I can start playing with it again!

 

You may find this thread useful regarding the P0171. Several things to check.

https://www.cherokeeforum.com/f2/cod...-still-131971/

 

Thanks. I had read that previously but re-read it just in case I missed something.

It was getting dark, but it appears that the wiring harness side of the upstream O2 has a wire that may be exposed.

After spraying the electrical connectors that I could find i started the Jeep. Typical hard start (long crank), smooth idle, then running rough (makes sense, since fuel mixture is off). I disconnected/reconnected the IAC - no change when revving or idle. Unplugged the TPS, died immediately. MAP hesitated when unplugged then acted like nothing had changed regardless of engine speed.

It doesn't smell like exhaust and it isn't loud, but after listening closely I may have convinced myself that I can hear an exhaust leak. Found an interesting thread where a guy used a (clean) shop vac to blow air into the exhaust while spraying the mani w/ soapy water. Seemed logical, might give that a go if our shop vac is clean.

 

Interesting trick with the shop vac.

I made a smoke generator out of a Harbor Freight heat gun (a whopping ten bucks), a 6" x 1 1/2" (or was it 1 1/4"?) galvanized nipple, a few odd fittings, a short section of rubber transmission hose, a section of wiki torch wick, and some baby oil on the wick.

The galv nipple fit right over the snout of the heat gun, the fittings necked that down to a 3/8" barb fitting, and the hose went over the barb. Soak the wick in baby oil, put it in the nipple, slip the nipple over the heat gun, and you are making smoke. Just a little bit of positive pressure - enough to fill the system and find the leaks, but not enough to blow anything out.

 

BlueRidge - that smoke was being blown up the tailpipe? Or was that to find vacuum leak?

Jeep is running rough enough I just left it at work and will be driving the bike until I get it fixed. Going to try the SeaFoam through the brake booster tomorrow. To my understanding the vacuum will suck the SF through the line correct?

Side note: if it is just the manifold gasket and not the manifold itself (assuming the new MAP doesn't fix it), should I replace both anyway? Jeep has 140k miles and no offroading until I got my hands on it...

 

Vacuum. Although, if you leave off the reducers, you could probably blow it up the tailpipe, too.

Yes on the Seafoam, but I don't think that will fix your problem.

I really like CR-Snow's suggestion. Get a Bluetooth OBDII and record some logs. I'm betting you'll see a problem with the O2.

 

OP,did you check for shorts on O2 and your overall grounds?

 

Madmanmarty - I have visually inspected the wires to no avail. However, replacing the MAP made a tremendous difference in performance and idle quality (changed it yesterday). Unfortunately, my second trip driving (as required to set the MIL) I got code P0171 and another that I can't remember - but it was O2 sensor low voltage bank 1 sensor 1. Thanks to CCKen (link for P0131 below) I'm gonna go searching for grounded wires..
https://www.cherokeeforum.com/f2/p0131-198788/

It should be noted that it's probably covered in crap already, seeing as my parking spot has a black spot the size of a bowling ball from me revving the engine while trying to fix..

New BAFX bluetooth came in and they suggest the torque app. So far I'm unimpressed. For one, the app stays on despite force closing.. Any better suggestions? (yeah I'll search the forum too)

It still has a stumble when coming to an idle after downshifting and performance is sluggish (not surprising given the fuel mixture) but far better than it was. Also, don't bother trying to clean your MAP - it'll just fry..

 

Havent found a short: all fuses and relays have been either replaced or moved.

Cant get torque to send me a log but thats a samsungS5 problem..

Runs pretty good and mpg is back but still idles rough occasionally.

Low voltage p0131 fixed when I changed the coolant sensor.

Fuel pressure at rail is 42 (run) max, 48 at idle

 

Had a weird combination of
1) coolant temp sensor (from overheating) was causing the voltage issue w O2 sensor because they are on same circuit,
2) bad MAP,
3) bad TPS,
4) bad gas.. don't by speedway in Hawaii apparently.. reset the PCM after all was changed and everything is running along fine..
now time for the roof rack, LED bar, HID lights, AC and radio..

 

Really! Good to know!

Glad it's feeling better!

 

I thigh I had it fixed bc the problem went away, then came back. Thought it was definitely a short but couldn't find it. I've got a bum shoulder so I had been looking one armed and mostly at dusk. Finally cut the harness lose from the zip tip holding it to engine block..



Hadn't chaffed at the usual spots.. Turns out the ground was actually at the harness... Other parts were likely good so I'm glad I kept them

Everything is straight right now.. On to the fun mods