This sounds like you may have an air leak in the intake path. There are quite a few possibilities, so I will start out with the most obvious and easy to check.
Check around the intake path for air leaks. The mass air flow sensor is mounted on the air cleaner assembly. There is a plastic duct going to the intake manifold. With the engine idling, listen for any sounds of air leaks in this area. You can verify a leak by spraying a bit of gum cutter/carb cleaner around any suspected leaks. If there is a leak, the rpm will increase.
Try unplugging the connector from the ISC motor on the throttle body with the engine idling. The engine should drop rpm or possibly stall when you do this. If rpm does not drop, you could have a sticking ISC motor.
Check for trouble codes. A bad coolant temperature sensor can also cause a high idle.
Also, be warned, if the throttle body has been cleaned, it is ruined. The engine will not idle correctly until it is replaced IF it has been cleaned.
Two things that you must NEVER do to a Ford since 1992 - NEVER clean the throttle body, and NEVER back out the idle stop screw. Either will ruin the throttle body, and it will have to be replaced.
Hope this gets you started in the right direction.
Monday, March 23rd, 2009 AT 6:47 PM