When the car is throughly warmed up unplug the IDLE AIR BYPASS VALVE. The engine should run around 500 to 600 rpms. If not the curb idle is not set right or their is excessive sludge in intake system. For more info contact me at firstname.lastname@example.org
The idle speed control valve is easy to remove only two bolts and an O-Ring seal but I have never "cleaned" one on a Ford, I do take apart the Toyota/Lexus ones but the Ford one doesn't come apart. Make sure there are no intake manifold leaks or intake duct leaks. Computer controls the idle speed, valve either fails or other conditions put idle control control out of the range the computer can pull back the idle.