1996 Mercury Sable car idleing to fast

This points to either a bad thermostat or coolant temperature sensor.

If the thermostat is not functioning properly, the engine does not reach proper operating temperature, and causes the code.

If the thermostat is operating correctly, but the sensor is bad, the computer THINKS that the engine has not reached proper operating temperature and generates the code.

Start be checking coolant temperature when the engine is running by maikng the following checks: The gauge should read within the brackets, with center of gauge the preferred reading. Heater should be operating at normal efficiency - good and hot, not lukewarm. Feel the radiator hoses - CAREFULLY! They should be uncomfortably hot. These checks should give a good indication of whether the engine is reaching proper temperature.

If the engine is up to temperature, then the coolant temperature sensor would be the probable cause of the problem.

Hope this is of some help.