The battery was week when I purchased the car 6 weeks ago. A couple days ago the car wouldn’t start. I replaced the battery and it started like it should, a lot better than with the old battery. I checked the voltage with the new battery installed and the car running. The voltage was 14.3 running and 12.6 stopped. After the car gets hot it starts stalling when coming to a stop. When cold it ideas fine, but the A/C has to be on. The car drives perfect until it’s time to stop or after you drive it and try to start it hot. It has 96,XXX miles and it’s an auto. Any help is much appreciated.

 

The idle air control (IAC) motor controls idle speed. It compensates for ambient temperature, engine temperature, AC load, power steering load, etc. The CPU feeds all this information to the IAC through four driver circuits. When you turn on the AC the IAC opens a larger inlet to the intake manifold. The engine speed increases.
Changing the battery should not have affected these drivers. However, when you disconnect/reconnect the battery the computer must go through a learning cycle. This process may take a few hours. To avoid loosing the computer memory it is wise to apply another 12 Volt source, like a battery charger, during the removal/re-installation of the battery. This will keep uninterrupted power.

 

Thank you for the help. What do I do at this point? Drive it for 2 hours, let it sit and ideal for 2 hours? Is there a reset? Thanks.

 

You may try to run the car to allow the computer to finish it's learn cycle. Or-- you can remove the negative battery cable and reconnect after 15 minutes. This should clear the computer and start the learn cycle.

 

Last night I let the car run for an hour and the problem is gone. It runs perfect. Thank you for your help.