Yo Dave,
If it is an EFI 86, try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @
http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded
http://www.fuelinjectedford.com/images/selftest03.jpg
Without a code;
IAC gasket trim by Nelbur @
http://broncozone.com/topic/22150-fast-idle-problem/?pid=115710
It's a long post, but may help.
Next time, please fill out your Signature with year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. for better responses.
Click your name in right black panel in upper right;
In pop up,
Click, My Profile
Click, Edit My Profile in right side black panel
In left panel, Click, Edit Signature
Enter info
Click, Save Changes