Jeep Questions

I have a 1998 Jeep Cherokee Sport with almost 114,000 miles. I have a couple of questions. I have owned the Jeep for 5 years. After I put about 50,000 miles or so on it (it had about 36,000 when I bought it), the Jeep would lope at idle for a few minutes. Sometimes it would stall. If it didn't stall after the loping episode the engine idle would go back to normal. If you drive it during the loping episode you would feel hesitiation in the accelearation during this time and then after a couple of sputters it would be normal. I took it to several mechanics and two Jeep dealers. Diagnosis ranged from bad plugs to malfunctioning fuel injection. Plugs were replaced and fuel injection was cleaned and a couple of other things replaced that I can't remember what they were. The problem was never fixed and I have been driving it like this for the past 3.5 years. It doesn't happen everytime either. And of course it didn't happen when I took it in for repair. Does anyone know what the deal could be? Any solutions?


Another question: Sometimes when I right from a stop the there is popping noise coming from the rear end. Almost feels like the drums are grabbing. Brake man said everything looks fine. What could this be?

Another question: I have heard that you should change automatic transmission fluid routinely and I have also have heard that this is nonsense. What's the general consensus on this? And what about differential and transfer case fluids?

Thanks

Have your CPS tested. Crank Position Sensor.

mje4130 said:

Another question: I have heard that you should change automatic transmission fluid routinely and I have also have heard that this is nonsense. What's the general consensus on this? And what about differential and transfer case fluids?

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Change your tranny fluid. 30-40,000 miles is a good interval. It takes Dexron/Mercron III, not regular ATF. This is also a good point to do the others at as well if they haven't already been done.

Differentials: can't remember what weight the gear oil is meant to be, but be sure to add friction modifier if you've got a limited-slip in the rear.

Transfer case: uses regular ATF with no additives. Should take about 1.3 litres if I remember correctly.

Brakes...98 Classic Up Country, 112k. If its any consolation, my jeep has been doing that on the left rear wheel for approx 70k. Started only after haven been driven an hour and on a left turn after a stop. Dealer also said everything was fine and I can't find anything either . It has worsened in 70k miles only to the point where it will sometimes occur starting out straight ahead on a hot day.

I had the same loping idle and stalling problem on my 2001 XJ. I also replaced my plugs, TPS sensor and cleaned my fuel system to no avail. I ended up replacing the two oxygen sensors before the catalytic converters as these control air-fuel ratio. This completely fixed my idle problems and increased my fuel mileage by almost 4 mpg. If you havent already replaced them, this is where I would go next. I used factory direct-replacement Bosch probes but they are kinda pricey.

Jeeperz83 said:

I had the same loping idle and stalling problem on my 2001 XJ. I also replaced my plugs, TPS sensor and cleaned my fuel system to no avail. I ended up replacing the two oxygen sensors before the catalytic converters as these control air-fuel ratio. This completely fixed my idle problems and increased my fuel mileage by almost 4 mpg. If you havent already replaced them, this is where I would go next. I used factory direct-replacement Bosch probes but they are kinda pricey.

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I'm not too good of a mechanic, but can the two oxygen sensors be replaced by a novice such as myself. And are you saying you replaced the two o2 sensors before replacing the catalytic converter?

Thanks.

mje4130 said:

I have a 1998 Jeep Cherokee Sport with almost 114,000 miles. I have a couple of questions. I have owned the Jeep for 5 years. After I put about 50,000 miles or so on it (it had about 36,000 when I bought it), the Jeep would lope at idle for a few minutes. Sometimes it would stall. If it didn't stall after the loping episode the engine idle would go back to normal. If you drive it during the loping episode you would feel hesitiation in the accelearation during this time and then after a couple of sputters it would be normal. I took it to several mechanics and two Jeep dealers. Diagnosis ranged from bad plugs to malfunctioning fuel injection. Plugs were replaced and fuel injection was cleaned and a couple of other things replaced that I can't remember what they were. The problem was never fixed and I have been driving it like this for the past 3.5 years. It doesn't happen everytime either. And of course it didn't happen when I took it in for repair. Does anyone know what the deal could be? Any solutions?

Click to expand...

Check for vacuum leaks as well - common cause of a "loping" idle. Check all vacuum lines, the base of the throttle body, and the intake manifold mating surface. Use a can of carburettor cleaner - with the engine running, spray a "fog" around everything suspect. The cloud will be drawn in and the idle will rise if/when you find it. I also retorque my manifold screws annually - I typically catch one or two working loose... VERY common on inline sixes in general!

mje4130 said:

Another question: Sometimes when I right from a stop the there is popping noise coming from the rear end. Almost feels like the drums are grabbing. Brake man said everything looks fine. What could this be?

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Check your universal joints - starting with the one at the rear axle. Grip the shaft/yoke/whatever to either side of the joint firmly, and twist in opposite directions. If there is perceptible movement, replace the joint.

mje4130 said:

Another question: I have heard that you should change automatic transmission fluid routinely and I have also have heard that this is nonsense. What's the general consensus on this? And what about differential and transfer case fluids?
Thanks

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Every other year is a good interval, unless you do a lot of towing. The AW4, NP231, and NP242 all take Dexron II/III fluid, and do not switch to synthetic in the AW4! I've gotten mixed reports from the field on that, but more of them are bad. Apparently, the clutches in the AW4 are finicky, and if they "get used to" dino fluid, they'll want to stay in it. The NP231/NP242 don't care - switch to synthetic at will. The AW4 typically wants four quarts for a "service change," but keep an extra handy just in case. The "filter" is a strainer screen - I probably check and clean mine every third time I drop the pan. There is a drain plug, so you probably won't have to (but you should the first time - to check and clean the screen.) Carburettor cleaner works for cleaning the screen. Also, there should be a magnet in the pan - clean it as well. It's going to look "fuzzy" - that's why you're cleaning it. It shouldn't look "fuzzy" when you check it after that (that's all iron/steel from breaking in the planetary gearsets.)

Your axles will take 75W-90 gear oil - 75W-140 in the rear if you tow. Don't forget to add LSD Friction Modifier in the oil if you have LSD (there should be a tag saying so,) and if you're not sure, add it anyhow - it won't harm anything. Usually, you add two ounces to each axle that has LSD.

And, if you're still curious, you'll find fluid capacities and torque specs for a 1997XJ up on my site (I don't have a 1988 FSM yet.) There's a link in my sig - click it, and then go into the Tech Archive to find out what you'd like to know. I just got a bunch of stuff from Dana as well, so I'll be adding to those sections over the next couple of weeks...

5-90

Sorry, let me clarify what I said. Newer Jeep Cherokees have a total of 4 oxygen sensors and 2 catalytic converters. Each converter has an oxygen sensor before and after it. The sensor before the converter controls air/fuel ratio while the sensor after each converter monitors the status of the catalyst within the converter. The catalytic converters themselves are 2 canisters that are actually part of the head pipe just down from the manifold. If you crawl underneath your Jeep and look up at the enigne and exhaust from the driver's side, you will see the converters and the sensors. To clarify, I replaced the 2 sensors that appear before each converter in the manifold pipe. These can be reached, by hand, from the drivers side of the engine compartment. It does take a little creative wrenching and some feeling around, but I was able to change them both in about 20 minutes. I am a broke college student with no special tools or skills and I thought it was fairly simple so you should have no problems. Hope this clarifies things..

Jeeperz83 said:

Sorry, let me clarify what I said. Newer Jeep Cherokees have a total of 4 oxygen sensors and 2 catalytic converters. Each converter has an oxygen sensor before and after it. The sensor before the converter controls air/fuel ratio while the sensor after each converter monitors the status of the catalyst within the converter. The catalytic converters themselves are 2 canisters that are actually part of the head pipe just down from the manifold. If you crawl underneath your Jeep and look up at the enigne and exhaust from the driver's side, you will see the converters and the sensors. To clarify, I replaced the 2 sensors that appear before each converter in the manifold pipe. These can be reached, by hand, from the drivers side of the engine compartment. It does take a little creative wrenching and some feeling around, but I was able to change them both in about 20 minutes. I am a broke college student with no special tools or skills and I thought it was fairly simple so you should have no problems. Hope this clarifies things..

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Ayuh - there is a socket for the HEGO sensor that makes it easier to change (it's an "extra deep" well with a slot milled down one side,) but a 7/8" wrench should work in a pinch - use the open end.

MAKE SURE the new sensor has never-seez on the threads, apply it if it is not there. If you have the means to check, torque to 20 pound-feet with never-seez. Don't install without - or you won't be able to get it out again easily...

They're easier to change when warm, I've noted. Also, changing the "after-cat" sensors will not affect your fuel economy (I think that was mentioned earlier...) but the "pre-cat" sensors sure as Hell will. The "pre-cats" are for fuel trim, the "after-cats" are to monitor catalytic converter function.

5-90

Jeeperz83 said:

Sorry, let me clarify what I said. Newer Jeep Cherokees have a total of 4 oxygen sensors and 2 catalytic converters. Each converter has an oxygen sensor before and after it. The sensor before the converter controls air/fuel ratio while the sensor after each converter monitors the status of the catalyst within the converter. The catalytic converters themselves are 2 canisters that are actually part of the head pipe just down from the manifold. If you crawl underneath your Jeep and look up at the enigne and exhaust from the driver's side, you will see the converters and the sensors. To clarify, I replaced the 2 sensors that appear before each converter in the manifold pipe. These can be reached, by hand, from the drivers side of the engine compartment. It does take a little creative wrenching and some feeling around, but I was able to change them both in about 20 minutes. I am a broke college student with no special tools or skills and I thought it was fairly simple so you should have no problems. Hope this clarifies things..

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Okay, I know exactly where those are. I guess I'll give that a shot.

Thanks again.