Odd bogging problem, really need help

[98XJSport]

Unfortunately Ive been trying to diagnose this problem since late fall, been in and out of garages, and nobody could find anything wrong. Damn sporadic problems. The advice I had gotten thus far through searching and asking was most of the sensors Ive replaced. Others I replaced because I knew they were bad through testing or breaking myself on unrelated problems. So pretty much its down to paying a dealership an exorbiant sum, replace sensors at my leisure, and now checking the fuel pressure at the rail as soon as the parts store gets a guage in. All xjs have the schrader valve correct?

 

[98XJSport]

Well for the hell of it I checked out my engine ground. I removed it and cleaned both ends and where they connect. This made my problem occur less frequently, and when it did happen again, it was far less severe. This is the first time anything ive done has helped matters. I noticed the ground cable is slightly frayed in the middle from being pinched against the fuel rail. So i agged a piece of 10 AWG wire I had lying around, that didn't make any difference. Is there other major grounds I should try cleaning? I think my sensors wern't grounding properly, giving me this untraceable problem. Any suggestions?

 

[98XJSport]

Also could having upgraded the altenator had any affect? I went from the stock 114 (i think) to a zj 140 last fall.

 

[98XJSport]

OK Im gonna kill the piece of shit. Worked well not bad for 2 whole days, today back to square one, practically undrivable. Tomorrow its the pressure guage, if that doesn't do it its off to the dealers or on fire rolling down a hill. Unless anyone has any suggestions in relation to the alt or ground, im done. I give up.

 

[Sig220]

I sure hope you don't give uP!!!!

I have a 96 that has the same sort of problem so I have been following your thread. I have changed the TPS and the camshaft positioning sensor.

My problem is a stumble after initial crankup when the rpm's drop so low the Jeep shakes after a few minutes it recovers and runs fine until shut off for a while and then recranked. Before I changed the above parts, it would stumble after initial start after driving 300 feet....almost like it lost fuel supply.

I have checked for codes with my Snap-on ODBII scanner and found nothing. I took it to a shop for a more in depth scan and found nothing. Fuel pressure was confirmed as good.

I was sure hoping you would find a cure that would be helpful to me!!! I will be taking it back to a shop for another check tomorrow.

So hang in there, you are not alone and we WILL find a solution.

BTW, my wife says it has to be the upstream O2 sensor...but I am saving that for last...if she is right, there will be a change of power in the house!!!

 

[98XJSport]

Thats what Ive been wondering as well, If I can't confirm anything with a fuel pressure check, thats the next step I guess. I figure it would be good to have the tools anyways.

The only code I can pull from mine is a pending 02 heater/sensor/catalyst problem not specified by my scanner. With a new downstream... that leaves the upstream.

Have you also had it start to act up on you when driving? Almost like you took your foot completely off the gas, then it comes back, then goes, etc? All while never moving your foot?

 

[BBeach]

Im gettin a similar problem when i have a cold start. It would start, and i dont normally just go within 5 seconds of starting, but when i did this, i started to chug and it would seem to connect. Then i heard a few quick thuds and clunks??? I have no idea what it is, but my jeep has been smelling like exhaust and fuel in the engine bay when i start it. Ive opened the hood before on a cold start and all i smell again, was exhaust and what smelled like unburnt fuel. Could it be that the cat hasnt warmed up yet and is sending mixed signals to the computer? Or is it that i have a crack/leak in the exhaust manifold/downpipe that is resulting in reduced backpressure? Any ideas would be helpful.

 

[Sig220]

Thats what Ive been wondering as well, If I can't confirm anything with a fuel pressure check, thats the next step I guess. I figure it would be good to have the tools anyways.

The only code I can pull from mine is a pending 02 heater/sensor/catalyst problem not specified by my scanner. With a new downstream... that leaves the upstream.

Have you also had it start to act up on you when driving? Almost like you took your foot completely off the gas, then it comes back, then goes, etc? All while never moving your foot?

In a quick answer to your question........YES. Like it just went to idle then comes back up. Hmmm, with you pulling a pending 02 problem, there indeed may be a change of power at my house!!! Getting kind of busy with the end of the week, but I think I will get an upstream 02 sensor and see if I can slip it by the wife....trying to save face, you know!!

Would that be chit or what if both our problems were the upstream O2??

When I git er done, I will post results for you.

 

[Sig220]

Im gettin a similar problem when i have a cold start. It would start, and i dont normally just go within 5 seconds of starting, but when i did this, i started to chug and it would seem to connect. Then i heard a few quick thuds and clunks??? I have no idea what it is, but my jeep has been smelling like exhaust and fuel in the engine bay when i start it. Ive opened the hood before on a cold start and all i smell again, was exhaust and what smelled like unburnt fuel. Could it be that the cat hasnt warmed up yet and is sending mixed signals to the computer? Or is it that i have a crack/leak in the exhaust manifold/downpipe that is resulting in reduced backpressure? Any ideas would be helpful.

Bbeach..don't know what year you have, but I wonder if your cat may have plugged up?? Also make sure you don't have a fuel leak around the injectors....a roman candle you don't need!!

The only sensor in the exhaust system that affects run ability that I am aware of is the upstream O2........the one before the cat. Downstream is for the emissions monitoring. Of course I am not an expert...just a parts swapper!

Funny thing is the 96 Jeep has 160,000 miles, 2WD and has its problem while my 92 4WD with 149,000 has no problems....actually scares ya with power but was not taken care of in its lifetime....smokes a little and was wrecked a couple of times

 

[BBeach]

Bbeach..don't know what year you have, but I wonder if your cat may have plugged up?? Also make sure you don't have a fuel leak around the injectors....a roman candle you don't need!!

Its a 98 Cherokee 4.0 4x4 AW4. Its a possibility for the cat, i have knocked it a few times offroad, as well as i hear a slightly clink every once in a while like somethings bounching around. As far as the fuel leak, i sure hope not. How do you check those?

 

[98XJSport]

Sig220, any luck with the upstream O2?

 

[Sig220]

98XJ, not yet....weekend got worse!! Went to the beach for the weekend and had to return after one night....a unexpected job came up, came back Sat and worked from 4pm until 6am this morning....oh well...some extra cash!!

Anyway, I drove my "deer lease" 92 Jeep 4wd....ran like a champ although I was off on the mileage guess.....161,000 now on the odometer. I have installed new front coil springs for a cheapo lift and have not done the rear springs, yet...so it was like uphill both ways!! Gotta replace the A/C compressor if anymore trips like that come up!!

The 96 was taken out on a area trip before I left....the "stall-no power" came up a couple of times....usually doing about 20-25mph after leaving a parking lot. No problems at higher highway speeds.

Now jury duty Monday....so should have time to do the 02 sensor first part of the week.

 

[98XJSport]

I won't have time till week after next, so keep me posted if there are any results. I was going to try cleaning it today, but its over 100 in the sun and humid, no thanks.

Gotta get it going, lots of good wheeling to be found, but my celica isn't gonna cut it...

 

[Sig220]

98XJ,
After a hectic week that started last weekend, I finally got the time to install the O2 sensor. I used a Bosch that I got for about $50 at a local parts store.

During the first test drive, no problems with the bog!! It will be taken out again shortly, but I think my wife had it right.......whoops there goes the power shift in the house!!

Just for reference the old O2 sensor was a grayish, ashy color. If anything changes after the second test drive, I will update.

But it looks like we may have a cure!!

In total, I changed out the following:

Camshaft positioning sensor.........no change.
TPS.........................................no change.
O2 sensor.................................change.

I also reset the PCM after each change and I never got an engine code.

 

[Sig220]

Okay, 2nd test drive (longer trip) and still no problem.

Yippee, I think we may have found a winner!!

 

[Rocketman]

ALL sensors are VERY dependant on one good part. THE ALTERNATOR. If it is flaky, and if you wheel it sure has that chance, SWAP IT OUT no matter what or how it "tests."

 

[Sig220]

It wasn't the alternator, this time Rocketman.

If it were, I would have had other symptoms. You would have to read all three pages to understand what 98XJ's and mine were. Needless to say, none were even hinting at alternator. But now that you mention it, I knew the battery and the alternator will cause the ECM to react funny when they are going bad.

It would be nice if a faltering O2 sensor would have set a code....wonder what the criteria is for them to do so?

 

[Nixt]

Oh, man. This sounds familiar...
Almost exactly the same symptoms - feels like off-throttle, then comes back - clack sound - and the long series of replacing sensors...
See http://www.naxja.org/forum/showthread.php?t=91204 for my lament, and the fixes suggested to me along the way.

After reading this thread, I'm swapping out that upstream O2 sensor and CTS tomorrow. Hell, what's a few more bucks at this point.

If it ain't running right by Monday, it gets parked and I go buy a new truck.
I am growing to HATE my heep, and that's just sad.

 

[98XJSport]

I am growing to HATE my heep, and that's just sad.

I know what you mean, but then when it is running good and impresses you with it's capabilities....warm fuzzy feeling all over again.

Thanks for posting back Sig220, will be trying a new sensor sometime this week! Hopefully that really is it on mine, after all this time its hard to believe that there is a simple answer.

Rocketman is right about the Alt. I was having CTS problems when mine started going bad. However when my problems started the Alt. was only like 2 months old and hadn't been in much water yet. Good point to remember though and if this crap is still going on, I think that might be my next target. I have the lifetime warranty he he he...