low idle and stalling

Hi, I have an 00 XJ with 250000km on it. I'm down in moab from Canada, and my jeep has started to have some weird issues. quite often when idling or crawling at very low rpms, the tach will drop to below 200RPM, then rev back up to ~750 RPM. Today when doing a slow trail, the jeep would do this except it stalled instead of revving back up. It did this quite a few times. we turned around, and it made the descent terrible since I had to keep one foot on the gas to keep it running and one on the brakes. It has also started sputtering and stalling at higher RPMS now. Before this trip, I just installed a new TPS, so unless the heat got to something I don't know if it is that. I'm not getting any engine codes at all over this.

It seems to happen intermittently when I'm not crawling or idling a lot. but when I'm on the trails it happens all the time. I cleaned the throttle body as well recently. I'm under the impression it might be the IAC but I don't know how to test that, and I don't necessarily want to buy a new one if it won't help.

It also doesn't seem to happen when the jeep is cold. Not idling properly makes rock crawling extremely hard. I'd appreciate any help you have. I won't be able to check back for a day or two since I won't have internet. Please let me know if you have had this problem and what you did to fix it. I don't want to stop jeeping on my vacation because of this! thanks

I would try refreshing all of the electrical connections by unplugging and replugging several times. Include computer connections and all sensors inclucing crank position.

LOAD TEST your battery.

The symptoms you describe can be caused by a marginal battery creating havoc with the engine management system. And yes, you CAN have a batter that is strong enough to start the engine but weak enough to give you symptoms.

Start there. Any parts store will load test your battery for free.

With Winterbeater and BirchlakeXJ on this--start with the heart of the system, the battery, and work from there out.

Ok i forgot to mention but I just bought a brand yellow top optima in Denver. I guess that doesnt mean that it still couldn't be defective, but I would like to think that the battery is ok. It's starting to sputter on the highway now as well... driving along at 65 and it will all of a sudden lose power. It will finally catch itself and continue somewhat as normal from there, but will still sputter now and again. I checked all the connections and replugged everything several times and it's still doing it.

The symptoms are still intermittent though... we just pulled over in some small town and it was idling decently at ~750rpm.

Ok, what was the issue that caused the yellow-top purchase?

Do you have your DVOM/DMM/voltmeter with you? What is the static voltage of the battery measured between the terminals? What is the voltage measured between the terminals with the engine running?

Have you been running any accessories when the issue presents--air conditioning, stereo w/amp?

well I bought the yellowtop because my other battery wasn't so good any more and i was anticipating doing some winching... The yellowtop should be good for that I figured.

with the engine running its 13.44V and with it off it is ~12.8V (just turned it off...)

We usually have quite a few accessories plugged in, including the 12v cooler and a laptop. And its been quite hot in moab so the AC is on as well as the radio and amp. Is it related to all the electronics and nothing is *really* wrong? I will try running with no accessories on and see if that helps at all. I feel there would still be a problem though since I think it 'should' be able to run with a few things going.

I also noticed today I got an O2 sensor code, I think it was P0135 and P0132 about the sensor heater not responding. I just replaced the downstream O2 sensor not too long ago either. But this could also be related to voltage; if the O2 sensor heater is not getting 12V it might throw the code too... I'm not too sure. Are these codes for the upstream O2 sensor or the downstream one? If they are for the upstream one, could a faulty upstream O2 sensor give me these problems?

As well with the TPS, I swapped it out with my brothers just now who is here, and my jeep still has the issue and his is fine. So I doubt it's the TPS.

Ok, from the voltage numbers it looks like you are charging good.

Did the shop put a full charge on the yellow-top for you or basically just off the shelf and install it?

Can you see the battery's production date on the label or case?

Optima charging info: http://www.optimabatteries.com/product_support/charging.php#yellow1

I bought it from four wheel parts performance, so however they gave it to me I just installed it. I'm glad the charging numbers are good, I was worried something like my alternator might be going.

I have found a fuse in my pdc was blown, and it was a 20A fuse for the O2 sensors (hence the DTC codes)... fuse 17 I believe. I replaced it and the codes went away and the jeep ran better for a bit, but now it's blowing fuses every few minutes. I visually checked the harness down to the o2 sensors and it looks ok... is there anything else this fuse feeds or is it just the two o2 sensor heaters? Is there any way to test the o2 sensors before I start buying parts?

I would think that if the o2 sensor heater was blown, I wouldn't be blowing fuses... What should I be looking at now?

Unplug the o2 sensor and put in a new fuse, see if that one blows.

joe_peters said:

Unplug the o2 sensor and put in a new fuse, see if that one blows.

Click to expand...

I did this, and it was good so I went and bought a new o2 sensor. so far the issue seems to be fixed, just fyi for those who might be having the same issues.

Ok, glad you got it (fingers crossed).

Post up if it turns out to not have fixed it.

Good luck.

Had the exact same problem! Started when I got to Moab as well, crazy! Replaced the upstream and it helped a little but it still cuts out every once and a while. It continues to throw the code for the downstream (135) but I didn't think that the downstream could have any effect on anything. Suggestions?