I have a 2001 4.6 4x4 with an auto tranny, here is the problem im having, sometimes it will idle at about 800 RPM's when it normally idles at about 600 RPM's when its in gear, and when i take it out of gear it will idle up to around 2000 RPM's by itself and i can shut the truck off and start it back up and it will run perfectly, any suggestions would be great, thanks.

 

Clean the IAC.