Hello I own a 2004 crown vic X cop car. At first it had troubles starting and i knew it was the spark plugs as we had not done a tune up in over a year IT IS RUNNING AT 2400 RPM STEADILY. So we changed the spark plugs, wires, intake gasket (which didnt need replacing), did diagnostic and no codes came up, there are no vacuum leaks, and injectors are fine and clean. Compression across the board is great. I hauls!!! Why is it idling SO HIGH. Im afraid its gonna blow. Please help we cant figure this out. Thanks

 

I might try to clean the IAC valve first to see if it changes the idle.

 

I would suspect the IAC control. When it starts to act up, the idle usually goes up.