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