The air/fuel ratio that's delivered through the carburetor when the engine is idling. It can be adjusted by turning the idle mixture adjustment screw(s) on the carburetor. The screw opens up a little passage that lets more or less fuel into the engine. On most late model vehicles, the idle mixture screws have caps that allow only limited adjustment, or they are sealed to prevent tampering. The relative richness or leanness of the idle mixture has a big effect on tailpipe emissions at idle.
© 2000 - 2002 Vincent T. Ciulla