I had to change the battery in my 00 this weekend as it was dead so I put in a new OEM battery and the car fired right up. Driving to work this morning I noticed when I came to a stop the car would idle really low, like around 500 rpm's and even try to die a few times. I had to tap the gas to keep the idle going.

Eventually as I got to work it seemed to idle around 800 rpm with the a/c on. Does the ECU just need to re-learn the idle speed when the battery has been out of the car for a few hours? The car was idling/driving fine before the battery change.

 

Got to ask:How long was the car sitting without a battery? Just repalced the battery in my '04 without issue.

 

Yep, the dead battery reset the ECU for you. Give it a chance to re-learn your driving conditions and it should catch on quickly.

 

The battery was out of the car for about 3-4 hours. And Jeffbrig was right, it a few cycles but it idles just like before now, the ECU had to re-learn.

 

the best way to do it is by letting it idle without load, a good 10 minute and it will learn itself again.