JustAGirl, here's what I found on an earlier post about "re-learning idle". It's just a copy and paste:
"You really simply have to relearn the idle. The computer remembers the proper IAC setting for idle. If battery power is lost, so is the setting. The surging is the computer searching for the proper setting.
Disconnect the battery, then run vehicle in gear for at least 10 min.
An easier way is to take it to your dealer and have them do it with a scan tool. Only have to let it get to running temp. so shouldn't cost much."
Hope it helps.