Jlewis

My wife left the car door open last night and the battery died. I tried to jump it today. It will start but it won't hold an idle. What could be the problem? I can keep my foot on the gas and it will hold at what ever rpm I hold it too? Let me know what you all think. Thanks.

RTorrez1

Try giving the battery a good charge. A weak battery can cause problems. If it is completely dead running the engine won't charge it enough. It will need to be put on a charger.

Fred/N0AZZ

If the battery was totally depleted the ECU may have to have a little run time on it to reconfigure all the settings like air to fuel, etc.. I think that is correct, if I'm mistaken someone please correct me.

A full battery charge would be required also like posted already.

Morat

x2
On my previous Jeep (a 96 if that is relevant) the alarm would drain the battery in a few days so I was used to this problem. I'd take the battery off the Jeep and charge it with a proper battery charger (one that can switch to float charging when the battery is nearly full).
Once you're ready to start the jeep, I found that I had to give it some throttle to hold idle and gradually back off the pedal until the ECU adjusted the mix to hold idle itself. This took a minute or so. Then I'd rev it up to 3k or so a couple of times before moving off gently and driving normally until it all smoothed out. Then a couple of full throttle trips to the redline and it was done.

tjwalker

This ^^^^

The #1 symptom of a marginal battery is stalling at idle.

Fully charge the battery. If problems persist, have the battery "load tested", (any parts store will do this for free) as sometimes a complete discharge like this on an older battery can be a death sentence for it.

Kingfisher

What they said!

When you rev it a little the alternator is supplying the juice!

Jlewis

Thanks and I got the battery tested and fully charged and it fixed the issue.

Kingfisher

Thanks for the update!.....

RTorrez1

I figured that was you problem when you said the battery was completely dead. But like tjwalker said "sometimes a complete discharge like this on an older battery can be a death sentence for it." So keep an eye on the elect system and the first sign of slow start or strange elect or running problem have the battery rechecked. Hopefully you won't have a problem.
Glad you got it taken care of.

michaelOH

This happens to me all the time.
I just keep the revs at 1500-2000 for five mins or until it holds an idle.