The IAC is the main controlling component for idling and when no trouble codes are present, it can mean the IAC is sticking intermittently. When IAC don't work well, turning the A/C on and off would make the idling speed unstable, at least momentarily. Try that to see if it makes any difference.
When it stalled, was it easy to restart?
Tuesday, May 28th, 2013 AT 7:19 AM