I have a 2000 Mercury Sable Wagon with the 3.0L vulkin engine. When I am stopped at a stop light the RPM’s go up and down, surging when the car is in drive and any of the climate controls are on (AC, vent, heat, etc.) when I turn off the climate controls the car is fine. No mater what when the car is in park it is fine (climate controls on or not). I have cleaned the throttle body, checked the idle air control module, I am not sure what could be causing it. The service engine soon never goes on. The car never use to do this. It only does this when the car’s climate controls are on in drive stopped at lights. Dangerous because the car surges. Any ideas?