gt problum

try cleaning out the iac motor. it is located on the side of the throttle body. use a can of carb cleaner. also, check for vacuum leaks....good luck!!!!

Is the car stock? Have you done anything to the intake? That can affect how it idles. Based on your comments though just as you describe, I would say it is running fine. If it is only hanging for a few seconds like that, no worries. Mine does the same thing whenever I have been driving at part throttle and I have a brand new IAC. Mustang idle is a figity thing and this issue is not causing any drivability problems, right?

Try cleaning the IAC, it can't hurt. Only cause you to burn maybe 30 minutes of your time. If you need instructions on doing this, let me know.

Also you want to check your check and perhaps clean your mass air meter. Make sure all connections are good.