what could possibly be wrong

[Nevada City Sparky]

Generally yes (high idle) but as I recall from my own experience a loose, INTERMITTENT vacuum leak at the throttle body connection hose (rubber peice that fits into the throttle body and attaches to the hose that goes to the MAP sensor) that goes to the MAP sensor can cause your problem.

Also it is not unusual to have two or more problems at the same time partially masking each other making the diagnosis almost impossible and some of the assumptions wrong.

Good suspect. Check the plastic line that goes from the throttle body to the MAP sensor. Perhaps the rubber hose at the MAP sensor is cracked or the rubber double hole connector to the throttle body is loose.

When we did my friends engine install we forgot to replace that line at first and symptoms were similar to yours--but worse.

Besides, its a cheap part to check and you can get a replacement "harness" at NAPA for like $10.

 

[Ecomike]

I am starting to think it might be a loose electrical connection. Could be anywhere in the ignition circuit but I would start with the battery connections and grounds first, then start checking, tightening up the wiring harness connectors (the female metal connectors can be tightened up carefully) at critical connectors first like the TPS, CPS, O2 sensor, intake air temp sensor, ECU, ignition control module, and then check the IAC and coolant temp sensor as well.

 

[Ecomike]

Good suspect. Check the plastic line that goes from the throttle body to the MAP sensor. Perhaps the rubber hose at the MAP sensor is cracked or the rubber double hole connector to the throttle body is loose.

When we did my friends engine install we forgot to replace that line at first and symptoms were similar to yours--but worse.

Besides, its a cheap part to check and you can get a replacement "harness" at NAPA for like $10.

Yap,

I have seen, had vaccum tube leaks that only leaked when you wiggled them, like when you apply the brakes and things move around a bit then they would disapear again. Leaking vacuum booster...mine only leaked when I applied the brakes, then went away if I let off the brakes. Thus they were intermitent, causing intermittent engine running problems.

Would a defective EGR, or intermittently defective EGR cause this problem? On second thought does it have an EGR, what year model is this beast anyway????

 

[j99xj]

what year model is this beast anyway????

1999 xj, obdII

By the way my new upstream oxygen sensor is in. Hasn't acted up yet, but only time will tell.

I will keep this thread going until I find what is causing my low rpm stumble stalling issue.

Stay posted. (and patient)

 

[XJ FREAK]

sounds to me that your torque converter is not disingaging and causing it to have a 1:1 ratio which in return cause this problem. 1988 had a non electric lock up it was internal. That is if the engine is running fine when it is in motion and has power loss below 40mph

 

[ifixit8]

It sounds like i have been having the same thing happening on my wifes 99xj. for me it's only when the car is warmed up, and if you get on the gas to pass a car. it just keeps on bucking/stalling, like the key is being turned off. I put in a new tps, and fuel pressure is 50lbs. took the car to a very good local shop and they say it's the distributor or crank sensor. I know the crank sensor is good because it runs fine. I am going to try a new distributor when I get the $$$ next week. no check engine light, but they pulled codes and one of them was a trans code. I just hope that it's not the trans. I still owe about 4k on the damn thing.

 

[j99xj]

I've made it over 24 hours without my problem with a new upstream 02 sensor!

I think we have a winner! (knock on wood)

I will get back to you all if I get the problem again. (after saying a few bad words)

 

[Ecomike]

It sounds like i have been having the same thing happening on my wifes 99xj. for me it's only when the car is warmed up, and if you get on the gas to pass a car. it just keeps on bucking/stalling, like the key is being turned off. I put in a new tps, and fuel pressure is 50lbs. took the car to a very good local shop and they say it's the distributor or crank sensor. I know the crank sensor is good because it runs fine. I am going to try a new distributor when I get the $$$ next week. no check engine light, but they pulled codes and one of them was a trans code. I just hope that it's not the trans. I still owe about 4k on the damn thing.

If it only does it when it is warmed up don't waste your money on a new distributor. Look at things that change with temperature. I would start with the O2 sensor. You can test your current O2 sensor with a volt/ohm meter while the engine is running.

Coolant temperature sensor and intake manifold Air temperature sensor can also be tested with an ohm meter.

Also check and make sure the new TPS sensor is not hooked up to the wiring harness backwards (like I did recently, which caused the same bucking and stumbling problem with mine)

 

[ifixit8]

If it only does it when it is warmed up don't waste your money on a new distributor. Look at things that change with temperature. I would start with the O2 sensor. You can test your current O2 sensor with a volt/ohm meter while the engine is running.

Coolant temperature sensor and intake manifold Air temperature sensor can also be tested with an ohm meter.

Also check and make sure the new TPS sensor is not hooked up to the wiring harness backwards (like I did recently, which caused the same bucking and stumbling problem with mine)

thanks for the ideas. i am pretty sure the tps is hooked up right, it has a plug that will only go on one way. i will be working on it with a freind tomorrow. we will check the cts and the o2 sensor. i'm thinking o2 sensor now, since that is a temp related sensor. I'll keep you guys posted.

 

[j99xj]

Crap...

It's doing it again.

But it went for almost 3 months with no problems with the new oxygen sensor.

Does anybody have any clues as to why this is happening AGAIN?

 

[langer1]

Crap...

It's doing it again.

But it went for almost 3 months with no problems with the new oxygen sensor.

Does anybody have any clues as to why this is happening AGAIN?

More bad fuel,have you been getting lots of rain?