Warm Jeep Won't Idle Well

a little help?

what year?engine?fuel injected/carbureted?computer?

Awww Geeze... Can't believe i left out the important specs.

Its a 2000 Jeep Wrangler Sport, with the 4.0.

Dirty- loose battery cables...... could be that the rain was the straw that broke the camels back.The jumper cables being removed was a clue that they were loose and the movement of them on the battery posts caused the symptoms you descibe. Any trouble codes?(check engine lite) if not probably cables..... hope I helped.....

the sarcsm is free.......

no codes, no check engine light.

Most often, the rough idle is caused by a vacuum leak. Could the sudden onslaught and torrential down pour of water and thus the water spashing under the vehicle have blown off a vacuum line and when you press the brakes the idle becomes rough?

If you have the famous Quadratrac vacuum operated shift transfer case, chances are, a vacuum line mounted anywhere along the line (inlcuding the interior switch) was knocked off.

Good Luck!

JL Mealer
Mealer Companies LLC
http://mealercompanies.com

The jeep must have finally dried out to the point that whatever was causing the issue, has resolved itself...

I recall from my college days a friend with a 70's vintage Toyota land cruiser- part of the emissions control scheme was that the engine seemed to be on a faster idle stop while the vehicle was moving, and the engine would go to slow idle once stopped. It had a stick shift. To drive it gave me the idea that it was never intended to "engine brake" at very low speeds. I didn't understand the emissions aspect, nor how speed was sensed, but I wonder if this is somehow related to your problem.

Good luck, sounds like you'll have accomplished something once you solve this one.

I have a Jeep Cherokee that had the same problems. The problem was due to a hairline crack in the solenoid (ignition) coil. A replacement coil did the same thing about two weeks after it was installed. The last replacement is still working after a couple of years.

As to why, I think that the resonant vibration at idle more closely matches the resonate vibration of the cracked solenoid so a momentary interruption occurs more often under those conditions. The warmth of the engine symptom also matched my situation.

Let me know if this helps!

no coil... it has some kind of fancy coil/rail thing, with no spark plug wires.

One Jeep guy to another I just want to say Congrats on it fixing it self and good for you to be out in it in the rain. I am a desert rat and we get very little rain. However when we get it we all head for the mud. I think your air filter is just on the edge of being too restrictive and the rain may have taking it to the air flow limit.

Thank you fellow jeepster, I'll pull the air filter tonight and have a looksee... I doubt that It could be causing a restrictive issue, as it is a Air-Raid intake, with a K&N racing filter, but I'll take a look none the less (not that I would be able to see anything as the water has all evaporated now).

Its also got one of those "Tornado" throttle body spacers, and a Banks Stainless racing exhaust.

I am absolutely sure that the Idle issue is strictly electrical, and I am also sure that The cause was not anything in the engine compartment, as I do live in Oregon, and drive on roads that looks like rivers on a regular basis in torrential downpours. this problem was absolutely due to the water finding its way into all areas of my dashboard via the absence of a roof.

What links the idle to the speed? What under the dashboard could malfunction to allow all normal operation and great performance, Idle while rolling, but not sitting still.

Not the breaks, not the battery, not the airflow... Is the only place they are connected in the OBC? IF so, might my OBC have gotten wet? Shouldn't it be in a sealed container of some kind?

Our jeeps are set up very much a like. And I am lucky enough to only get into ground water and some sandy mud. I am envious of your area but I could not give up rock crawling.

If you want to see my area look at You Tube -PNO- rock bottom. My Rubicon is the white one.

The club site is PlayNiceOffRoad.com. For some water pictures....and no Jeeps don't float.

LoL... "and no Jeeps don't float"

I hope to never find that out for myself, But i'll take your word on it.

Look at the throttle-position encoder. Its a potentiometer on the end of the butterfly valve. Good test is if you nudge the accelerator and can keep it running smoothly, the pot is crudded up on the low end. Talk to the guys at Autozone, et al. Easy to diagnose...

Also - slightly related topic: On the Jeep, if the battery has been disconnected or discharged to nothing, when you get it started - it won't run; need to depress the accelerator for 5 minutes or so until the ECM (engine computer) gets its act together.

Hope this Helps

Lynnbob33

I would have to agree with your thought of the on board computer. You might want to remove the connectors on it ans reseal with some water resistant compound designed for this. Good luck.

it could be the O2 sensor - too old, too loose? or a wire fell off it? if its not sending the right message (air gas mixture) will throw everything off.

Well, A while back I removed All the ground connection on the vehicle, cleaned and replaced. Also cleaned the battery terminals... Problem gone, I think all that water just caused some corrosion buildup on my grounds, causing some strange Electrical activity. Seems to be running perfect again.... Well, Except that squeaky belt in the morning.

I get to go put the hard top back on tonight... I fear the Oregon rainy season (Sept-June) is just around the corner.

Thanks for the help!