First suspect is the IAC (Idle Air Control) valve needing cleaning. It is a computer-controlled valve whose only job is to manage the idle. They get gunked up and start what you're seeing. Located just below throttle position sensor on the throttle body. Remove and clean with throttle body cleaner. Clean throttle body while you're at it - follow directions on can.
I've read that EGR problems can cause idling issues, but others here know a lot more about that than I do. Yours being an '02, not sure if it even has an EGR (they eliminated it at some point in production).
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs
Last edited by peva; 07-11-2011 at 07:48 AM.