Throttle Positioner System: Operation: Starlet
The throttle positioner system is vacuum controlled. When the engine is cold, a bimetal vacuum switching valve (BVSV) is open and holds the positioner in a set position. When the engine is warm, the throttle open and vacuum at the TP port is low, the positioner is also in a set position. When the throttle is released, as during deceleration, the positioner keeps it from closing completely until vacuum bleeds through the jet restrictor. The high vacuum present at the TP port will then pull the positioner back and allow the throttle to close completely.