Sounds like moosing due to a sticky IAC valve.

Try cleaning the valve and resetting idle. If that doesn't get it, install the TH fix and be prepared to replace the IAC valve with the updated Ford unit.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!