Yesterday I left the lights on my car on for about 1 hour while I went in to eat dinner and when i came out the car was dead. This can be expected, but it has never happened before. So i got a jump and it started right up and every time I have gone to start it since it has been dead, I brought the battery out and charged it then put it back in, noticing that one of the cells during charging was not bubbling. But i got it back in and it started up and I drove it and it seemed like the when i come to a stop the car goes down to about 500rpms then back up to 750 rpms. So i'm wondering does this sound liek a bad battery problem, would a bad battery cause idling problems, or is it more than just the battery? Could i have messed something up by jumping the car, did leaving the battery out of the car for an hour possibly change the computer so it has to relearn how to run properly again? Any help would be greatly appreciated...

 

Have you checked to make sure the Alt. is charging?

A battery will make the car go wacky the entire car is networked.

And yes the computer may have to relearn.

 

Same thing happened to me too.

I had to change the battery (over 5 years old) and when I checked the voltage from the alternator, it was showed 12 volts (which meant the alternator was not charging)

Normal voltage from alternator (with car running) should be between 13.5 and 14.5.

Had to get a new alternator and once replaced, car ran great.

Hope it helps

 

I went and had the codes pulled nothign then I went to an electrical place they tested the battery and altenator and no problems with either. The guy said the battery is low but good and the only thing diagnostic computer came back with was a drain somewhere in the car. Im gonna give the altenator an "educated tap". Since i took the battery out yesterday charged it and drove around a little the idle has returned to normal and it hasn't shut off on me. MAybe just some freak thing? I don't know, I'm really used to electrical problems being a long time audi/vw fan, so this isn't going to keep me down too long.

 

okay checked the altenator, its fine, I did some battery maitenance i.e. added water, cleaned the posts, and checked all my main conections. Idling went bad again but i neglected to say that after a couple drives last time it went back to normal. So i'm guessing it will do the same, I'll see where this gets me, but i suspect a new battery is needed. I have a sneaking suspicion that there is in fact a dead cell on the battery, which could cause a drain. More info later.

 

in case anyone cares it ended up being a bad battery, had one dead cell that was creating a drain.

 

Glad you got it figured out.