My 5.0 F-150 idles high quite often, and sometimes it idles fine. A lot of the times, when i'm going down the road and shift into the next gear the idle will shoot up from 2500-3000rpms. It will stay there for a few seconds then remain to have a high idle until I shut it off, or until it just randomly goes away, any suggestions?

 

idle air control-what year is it ?