If it's been 3-4 years since you've replaced the battery and you find yourself needing one as I did, be sure to take it to the shop and get the throttle body cleaned out. It's a $40 job that will allow the transmission to "reset" itself to your driving style. If you're experiencing a surging or very low idle (low enough that it stalls), do this cleaning. It has to do with the mass air flow sensor located in the throttle body.