Loping 03' F-150

Eractic idle is often caused by tps not giving a steady voltage at a given position. Also any vacuum leak will let unregulated air into the intake thus raising the idle, the engine computer will detect the over rev and cut the fuel thus causing the surge up and downand the computer tries to keep the motor from dying. Ford has had some issues with those plastic instake craking and leaking or just not sealing. Check for vacuum leaks from top to bottom.