2006 Chevy Cobalt: Battery keeps dying after sitting over night or for more than a few hours. Battery and alternator test came back good.. What could be the problem?

SOURCE: 1999 bmw 528i replaced battery and alternator

Replace your battery when its being tested there not testing it under a heavy enough load. A battery could have a dead cell in it and still show good on the charger. I've had that problem a few times.

SOURCE: my 2006 chevy cobalt 2.2 liter sputters

Fault with the IAC valve.there maybe a trouble code associated with it also./ Go to your nearby autozone or auto parts retailer and ask them to put a scanner to the car....make note of the codes if any are found. the IAC valve i usually locate don the throttle body and can be removed for inspection and sometimes cleaning using a good throttle body cleaner spray and a pipe cleaner brush.