What does it mean when a car is running to rich?

Answer 1

If a car is running too rich, the air to fuel mixture is not right. Running rich means that there is too much fuel (gas) going into the engine for the amount of air going in. On the opposite side, too lean would mean that there is not enough fuel going in for the amount of air. Cars can run rich when the oxygen sensors go bad, or on older cars, if the carburetor is not adjusted properly. Running rich can be accompanied by a distinct exhaust smell, and in the extreme cases, some blue smoke. The inside of the exhaust pipe will be black if a car has run rich for any amount of time (when it's cool, take a light colored rag and wipe it inside the end of the tailpipe-if it comes out black, the car is probably running rich).