• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Suuuper Low Idle: New Alternator?

CherBear

NAXJA Forum User
Location
Indiana
Yesterday I had left my running lights on for the night by accident and had to jump start the jeep in the morning. It started up fine, but would idle very low. 430~ per scangauge II. I figured that since the battery was low maybe it was just causing problems with the ignition. I drove it around long enough to recharge the battery, but still has the low idle problem. When I am driving, my volt meter will read about 13.5V (also verified by scangauge). It cranks and starts every time, but will still always settle into this really low idle. Just as a test, I let it sit at idle for about 3 or 4 minutes in D, with foot on brake to see if it will die, it does not. If the AC is turned on, it will idle a little better, but still not well.

The alternator was my first suspect, I am taking it over to AutoZone tomorrow to have them test the Alt output. Is there anything else I can check in the meantime?

I am going to reset the engine computer to see if that does anything... My ecu has a few quirks.

All help is appreciated! Thanks in advance.

-Cher"Sounds Cammed"Bear

EDIT: 2000, 4.0, AW4. Battery is 5 yrs old. Alternator is stock. 135k miles.
 
Well it seems to have "healed" it's self... I am not sure how. Chalk it up to the ecu readjusting to sensor input? No idea.
 
Sounds to me like the computer just had to "learn" how to idle again...
I had same issue when I changed my battery the last time.
 
It may be computer relearning, or also the effect of the battery itself. Some ECU's dislike straight alternator output, which is what you often get at least for a while after a boost, until the battery recovers.
 
Back
Top