2001 Jeep Cherokee - stumped

[HawkeyeScott]

Same problem I posted about around Feb. 10. So far I have cleaned the throttle body and IAC and replaced the throttle position sensor. TPS was little more than a $52 guess.

Sadly, the Jeep is still running rough - mostly at idle but not nearly all the time. Twice now it has cut out on me at highway speeds. Push the gas and nothing happens. Running but only losing speed. Then, once the RPMs rebound, it's fine. Seems like if I stayed on the gas 100% of the time, I wouldn't see the problem. Only seems to show up at idle or when coasting. Very sporadic too. Will go days in between seeing the problem. Thought maybe today I heard some added sound - air noise? - at higher RPMs. I've seen vacuum lines as one potential fix but I'm not sure. I may be hearing things.

It did throw an O2 sensor code today. Has done this once before and my mechanic wasn't convinced that was actually the problem. MPGs about where they should be. Would a bad MAP sensor throw an O2 code? I bought an O2 sensor and now can't get the old one unstuck. Sprayed WD40 on it. May try it again tomorrow if it the WD40 doesn't burn the whole thing up first. Feel like I'm just throwing another part at it though.

Getting frustrated. Don't want to throw money at it but not sure where to go. Getting the car to my mechanic can be a pain since he is so packed, and is he really gonna do anything but guess like I am?

Thanks for any help.

 

[zrxkawboy]

Didn't see your original post, so maybe this was covered, but have you checked the fuel pressure?

 

[HawkeyeScott]

Have not. Read that as a suggestion on another forum. That might make a lot of sense though.

 

[tomcat27]

I too, hate throwing parts at a problem without thorough diagnosis. I did once have a problem with my dakota where sometimes it would run fine - sometimes bog down and barely accelerate - sometimes it would only go 20-30 mph. after many months it finally threw an 02 sensor code. new sensor - ran great ever since.

 

[JimPghPA]

I am not familiar with that engine and year, but one of the things that comes to mind is a bad vacuum advance on the distributor. I don't even know if your engine at that year has a vacuum advance, but if it does and it does not go to correct setting that would make engine stall.

What could be going on is the advance could be going to advance when you throttle up. Then if it did not go back down when the RPM's drop the ignition would be firing too early. That would make it run rough, and possibly stall.

If this is the problem fix could be as simple as lubing up the advance part of the distributor, including the spring, or as complicated as replacing the spring, or even the vacuum advance, and or distributor.

It would be great if you could get a friend with identical engine to swap out things like distributor and then try it. Probably just wishful thinking, I know.

 

[HawkeyeScott]

This set up does not have a typical cap/rotor set-up. The distributor basically sits right on the plugs on the side of the engine. (Inline 6; 4.0) And unfortunately, I have no friends. Just you guys.

FWIW, drove the car to work this morning...no problems at all.

 

[GMBoy]

I had a 2000, similiar to yours with the coil on plug design. Absoutely loved that truck and regret selling it. Anyways - you could have the coil unit breaking down since it is an intermittent problem. The Map sensor can also mimick this situation. Since you already have the 02 sensor - go ahead and install it. That cannot hurt and may actually be starting to fail on you. You don;t mention the actual code so I can't elaborate anymore on that. I do still have my factory manuals so I could PM you if you need more help.

 

[HawkeyeScott]

Thanks everyone.

GMBoy, I don't have the printout from AutoZone in front of me, but I think it was the 0132 code. I googled that just now and it jives with what I remember reading on the printout.

 

[eljefino]

Is the gas tank near empty when this happens? That design has the fuel pickup in a funny place, IIRC when turning left starves it of fuel. Maybe some pickup extention fell off etc in the tank?

 

[HawkeyeScott]

Nope, it happens when the gas is at any level.

I feel like we're playing 20 questions.

UPDATE: Just replaced the IAC. My mechanic has said that all along. Called him again this morning and decided to go that route. Will return the O2 sensor.

Fingers crossed,

HS

 

[VNTS]

did you do the key dance for codes???


Originally Posted By: HawkeyeScott
Nope, it happens when the gas is at any level.

I feel like we're playing 20 questions.

UPDATE: Just replaced the IAC. My mechanic has said that all along. Called him again this morning and decided to go that route. Will return the O2 sensor.

Fingers crossed,

HS

 

[Gary Allan]

Originally Posted By: HawkeyeScott


I feel like we're playing 20 questions.

UPDATE: Just replaced the IAC. My mechanic has said that all along. Called him again this morning and decided to go that route. Will return the O2 sensor.



I don't see how the IAC could explain your highway issue. It would merely, at worst, appear like an ever so slightly more open throttle. It has no ability to shut your engine down or rob it of power. It would work for the idle end of things in that it might not be able to compensate and effectively handle the idle. There you should have, assuming it was fixed in position, varied idle quality based on load (power steering/ac input) and engine operating temp.


..but good luck

 

[mechtech2]

Prepare for a fuel pump.

 

[zrxkawboy]

Originally Posted By: mechtech2
Prepare for a fuel pump.


Hate to say it, but that's my gut feeling, too.

 

[HawkeyeScott]

Hope you guys are wrong!

(But I am prepared. Just ready to get this fixed. Gotta remember that I'm $155 into this now and a fuel pump is another $120. That's still less than a month's payment on a new car. So I'll keep after it until it's licked.)

 

[hsd]

I say its the primary O2 sensor based on the code it threw and my own Jeep experience. My sensor was shorting out intermittently and causing it to cut out at highway speed then recovering as the ECM switched to open loop mode. You can test the O2 sensor theory by unplugging the O2 wire harness temporarily and test driving it. If the problem has gone away (except for a CEL)you found the problem.
Be sure to use a genuine Mopar replacement sensor to prevent other drivability problems. Guess how I know that

 

[1 FMF]

I have a 2003 GC with the inline-6 4.0L.
it would die on me while driving at 30-40mph in some instances, other times the engine would cut out and stumble and lose power.

the problem was the wiring harness that comes from the computer on the passenger side firewall, where it runs around the back of the valve cover and goes to the injector rail. What happened is the wire harness was sitting on the valve cover stud, and after 7 years and 50k miles the stud wore into the harness and shorted 3 wires to ground. I believe all inline-6's will have this problem because mine was stock and that's how they routed it from the factory. You may experience some different problems than I did depending which wires get chaffed and shorted. I never got an engine code and the engine would stumble at first but never stall. Eventually the engine would only run for 10-15 minutes if i just let it idle in my driveway then die, and the kicker was when the engine started actually dieing the SKIS light would come on and prevent restart for about 20 minutes. What was happening is the wire short would reset the computer which prevented it from ever storing any trouble code, and also set the SKIS. I sent it to the dealer thinking it was a SKIS problem but they found the wire harness short pretty quick, fixed only that, and that fixed everything.

if it turns out to be this, please email me.
simply feel the wire harness as it runs around the valve cover to the injector rail and see if either valve cover stud back there has poked into the wires.

http://www.jeepforum.com/forum/f13/2003-...bilizer-943258/

 

[mechtech2]

Obviously, since an O2 sensor code was given, it could be an O2 sensor!
But O2 codes before and after the cat are thrown for all sorts of reasons.

 

[HawkeyeScott]

By the way, I did check fuel pressure, which was fine. 6+ months after the initial problems arose, I think I may have licked it by replacing the two upstream O2 sensors. (Did them seperately. Used a Bosch from Autozone. Then did some reading and special ordered the second one from O'Reilly's.)

Lesson learned, try the easy, cheaper parts first. If it's on O2 sensor code, start with the O2 sensors!

 

[Challenger71]

Hawkeye, I am willing to bet that you also have excessive carbon build-up in your combustion chamber. Recommend buying CC cleaner to clean the valves & intake tract. I've got a 2001 with original O2 sensors and still runs as well as the day I drove it off the lot (117K ago). Consistent 18mpg city / 21+mpg highway.