So my Jeep has 211k miles on it. Last year it started stalling on the road and wouldnt start back up, after letting it cool off for about 30 - 45 minutes it would fire up again. I found out it was a short circuit in the crank position sensor so I replaced it, and it ran like a champ for over 8 months.

Then out of nowhere about 2 months ago the check engine light came on its giving me P0172 and another code both related to o2 sensor and mixture. I bought a new primary O2 sensor only to find out the previous owner replaced the stock OEM sensor with a wire in generic. So i spliced the OEM O2 sensor in its place.

Funny thing is there is only one sensor on this jeep, I have never touched the sensors since purchase and the primary O2 sensor is AFTER the CAT. Why is this?

The check engine light wont go out, even after the sensor replacement.

Now this last few weeks have been horrible. When I drive on the highway randomly it will just start smoking a little here and there and the RPMS will start jumping and surging like its preventing a stall or something.

If i put it in neutral it just puts and sputters and then dies. I have to press the gas pedal a few times and wait 5 or so minutes and it will fire up, this will just keep happening.

IF it starts to sputter and I just hold the gas pedal down or try to coast, it starts backfiring like gunshots. This is where I believe the engine has actually stalled but being in gear at 70mph keeps everything turning while the spark plugs randomly fire.

After 3-4 long bouts, I usually can make the rest of my commute with no issues.

If i brake really heavy or run the radio loud it "seems" to make things worse. Going over really bad bumps that shakes the jeep hard seems to do this as well. The battery is kind of weak and if I leave the lights on for a hour or so, I will need a jump. Alternator is definitely working as it charges the battery.

I was told something to do with the ignition module.

I am thinking about selling it now. Anyone have any ideas?

EDIT: I run royal purple 10w30 and Mopar oil filter every 4k. I also change the tranny fluid every 10k. I run ATF+4. I also use lucas tranny stabilizer as well. I did a oil pan service replacing the gasket and filter @ 204k.

 

You most likely need a fuel pump. Replacing the O2 sensor because of a lean code makes no sense. Codes don't tell you to replace parts, they only offer clues of were to start looking. Lean codes mean one of two things, not enough fuel, or too much air. Check the fuel pressure.

 

I just went and checked and I have a P0171 code. At some point in the past I believe I had a P0172 and P0135 or P0136 I cant remember.

I dont know why this car has one O2 sensor. There is a small hole in the exhaust about 3 inches away from the O2 sensor headed towards the rear of the car, after the O2 sensor.

 

The primary 02 sensor SHOULD be in the downpipe just after the exhaust manifold. The secondary 02 sensor just monitors the effiency of the cat. I also don't know why you don't have a primary, but if you don't, I wonder why the PCM allows the engine to run at all.

This is on the 4.0. The V8s may have two primaries. IDK. The downstream 02 sensor in my 97 was actually in the outlet of the cat. The wiring for the sensors is different.

A little help here. What year and engine size do you have?

 

Look for the ground wire to the computer. I had a 2000 gmc that had the ground wire break and bounce around giving me fits for 2 months. It was the thinnest wire in the truck.
HTH
DON TX

 

I have been dealing with this very same issue with stalling/backfiring & the exact details that come with this issue as described.I am frustrated with continuing replacing the ignition coil,02sensor by the cat etc...the last recent backfire split my muffler along the whole seem.I replaced the muffler & two days later the first backfire completely split the muffler's seem on the end of it this time.My mechanic is baffled & thinks the issue is in the computer system.He suspects the computer is not getting the full signal at times & this is why it triggers these issues.His reason is because we just replaced the 02sensor & the ignition coil just 1 mo. ago.I want to here from anyone that knows the solution here.I am exausted with replacing parts that don't need to be replaced.I don't mind replacing the computer...but as long as this is really the true problem because it's not a cheap fix.Bottom line...HELP...I want to solve the real problem.I love my Jeep,just not loving playing the guessing game...it's far too costly.Please someone help!

 

The only thing I can add is THAT type of backfire is caused by an interruption of ignition and a cat loaded with fuel. You may have a break in one of the wires in the ignition system that is hidden inside the insulation. This type of break used to happen a lot with the old point systems with the wire connecting the points to the distributor terminal. I haven't a clue when yours is.

 

It cost me @ $200.00 to replace my ecm (computer). I can find the address if you want.
DON TX

 

At this point, you probably need a new cat, too...