A description of throttle hang would be that the RPM stays up after releasing the throttle for a few moments. This is done for emissions purposes. Keeping the idle high for a little bit helps burn up excess fuel to keep the tailpipe reading cleaner while slowing down.
It is generally felt that the Contour engineers somewhat overdid the throttle hang, and it can be more pronounced than intended if the computer has mislearned, if the idle air control valve is sticky and slow to respond and if there are other electronic malfunctions that provide the wrong signal to the idle air control valve.
Throttle hang is not a new concept. Even in the days of carburetors mechanism were used to slow down the throttle return to idle. The most common of which was a dashpot that could be adjusted to alter the throttle closing. Originally it had more to do with preventing engine stalling when slowing down but later was also used to cut emissions.
