What is the purpose of the map sensor? What exactly does it do? Manifold Absolute Pressure....means....? I am asking this because my car has an idle problem. When i have the vacuum lines hooked up properly the car smokes a rich black smoke. it also eats gas. When i have the lines switched a tad it makes my idle go to 3000 or 4000 rpms. but no black smoke. could this be my map sensor?