How do you adjust the idle on a 1991 Geo Prizm?
These is a little metric set screw on the semicircular cam at
the end of the throttle cable. It has a locknut that will need to
be loosened for the adjustment. -On my geo, there is a flat-head
screw on the intake manifold, right next to where the hose is
connected from the airbox. Simply turn it right or left to adjust
your idle. Hope that helps-