rough low RPM idle . . . alternator? - Automotive Wiring and Electrical


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rough low RPM idle . . . alternator?

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mbrezin
New User

Jul 26, 2009, 11:29 PM

Post #1 of 5 (4587 views)

rough low RPM idle . . . alternator?	Sign In

2005 Subaru Forester, manual trans. I left a ceiling light on and the battery died over 8 days in airport parking. I got the car jumped. It started OK, but on the second try. Car seems to run OK, but frequently stalls out in low RPM. Alternator light is not on, but a friend tells me it's probably the alternator. Car ran fine up until battery death. Any thoughts on next steps? Thanks

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 27, 2009, 12:19 AM

Post #2 of 5 (4581 views)

Re: rough low RPM idle . . . alternator?	Sign In

No, the alternator is likely fine. The battery may have problems holding a charge if it was brought down that low. The stalling is due to the engine computer losing it's stored memory with the dead battery. It should relearn the idle strategy after a short period of normal driving. If it doesn't, try disconnecting the battery again and let it start over.

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mbrezin
New User

Jul 27, 2009, 2:13 AM

Post #3 of 5 (4574 views)

Re: rough low RPM idle . . . alternator?	Sign In

Thanks very much. I have the original battery in the car so I think I'll replace that and then see if that makes the computer happy.

Sidom
Veteran / Moderator
Sidom profile image

Aug 2, 2009, 1:56 PM

Post #4 of 5 (4554 views)

Re: rough low RPM idle . . . alternator?	Sign In

???????????

mbrezin
New User

Aug 2, 2009, 10:53 PM

Post #5 of 5 (4548 views)

Re: rough low RPM idle . . . alternator?	Sign In

Maybe it was a Savannah sparrow buzzing in my ear, but I did get motivated to check my battery and the test came back that it was pretty close to dead. I did buy a new one and after 5 miles or so of city driving the rough engine at low RPM was gone. Car drives fine now. Thanks for the advice!
Mike Brezin

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