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Discussion Starter · #1 ·
I accidentally drained my battery last night by leaving my aftermarket heated seats plugged in the power outlet for a few hours. Needed a AC battery charger to jump it back to life.

Now, my idle seems quite weak. As if it is about to stall when at idle.

Any ideas why this is happening and how to correct it??

Thanks in advance!!
 

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2004 Jeep Wrangler
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I accidentally drained my battery last night by leaving my aftermarket heated seats plugged in the power outlet for a few hours. Needed a AC battery charger to jump it back to life.

Now, my idle seems quite weak. As if it is about to stall when at idle.

Any ideas why this is happening and how to correct it??

Thanks in advance!!
With a dead battery, they won't idle at all once the jump start battery is removed. With a weak battery it will barely idle once the jump start battery is removed.

Nearly all modern alternators including all modern Jeep alternators absolutely require a good strong 12v from the battery to produce power. The days of being able to run on a dead battery are absolutely over for most cars and all Jeeps built since the late 80's. The reason being that few modern alternators are "self-exciting" any more... they require 12v from the battery to power the alternator's exciter circuit which is needed for it to be able to produce power.

Your alternator won't have the power from your weak battery to be able to charge the battery, those days are long-gone too. You need to use a bench charger and charge your battery overnight to fully restore it. Not for a couple hours, over night.

And completely draining a battery is really bad for it, they never recover 100%. Each time a battery is drained it loses a little more of its battery capacity.
 

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Discussion Starter · #5 ·
With a dead battery, they won't idle at all once the jump start battery is removed. With a weak battery it will barely idle once the jump start battery is removed.

Nearly all modern alternators including all modern Jeep alternators absolutely require a good strong 12v from the battery to produce power. The days of being able to run on a dead battery are absolutely over for most cars and all Jeeps built since the late 80's. The reason being that few modern alternators are "self-exciting" any more... they require 12v from the battery to power the alternator's exciter circuit which is needed for it to be able to produce power.

Your alternator won't have the power from your weak battery to be able to charge the battery, those days are long-gone too. You need to use a bench charger and charge your battery overnight to fully restore it. Not for a couple hours, over night.

And completely draining a battery is really bad for it, they never recover 100%. Each time a battery is drained it loses a little more of its battery capacity.
Great info. Thanks Jerry! As I said above, I've got it on the charger now.
 

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Discussion Starter · #6 ·
Had it charging all night. Idle is better, but not perfect. Seems to almost stall about 1 out of 10 times when at idle. I'm guessing it needs more charge?

Also, my aftermarket radio is symptomatic. The lights are dimmer than before the battery drain. I checked the brightness setting and it is set to the brightest level. Is the radio not getting the proper voltage because of the battery drain???
 

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I'm going to add to what Jerry said.
I forgot to put the tender on my battery last winter.
The Jeep started fine but locked the transmission into limp mode
This in turn sent me into panic mode because I just had everything redone the year before.
My battery is one of the older Diehard Platinums which is getting long in the tooth.
It's getting replaced next spring as it is 6 years old.
Bad batteries wreak havoc on Jeeps.
 

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2004 Jeep Wrangler
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Had it charging all night. Idle is better, but not perfect. Seems to almost stall about 1 out of 10 times when at idle. I'm guessing it needs more charge?

Also, my aftermarket radio is symptomatic. The lights are dimmer than before the battery drain. I checked the brightness setting and it is set to the brightest level. Is the radio not getting the proper voltage because of the battery drain???
With that I'll suggest you remove the battery and take it to a battery specialty shop and request they do a "load test" on it. A load test is the only way to know a battery's true state of health. The load tester will place a heavy load on the battery for at least ten seconds and then test its voltage. A bad battery will lose too much voltage after a heavy electrical load is placed on it. A common volt meter can still measure 12v on a bad nearly dead battery.
 

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For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.
 
The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving.

A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics. A poor ground at the ignition coil can also cause similar symptoms.
 

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Discussion Starter · #10 ·
I'm such an idiot. I took it to my mechanic. Turns out the radio issues were caused by some radio settings that were reset when the battery went dead. There was no issue relating to the battery and the radio. Looks like I'm good again. Thanks to everyone for the input!!!
 
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