1978 Throttle Positioner Systems

All models, except Cressida (4M engine), use a speed controlled throttle positioner system. A vacuum switching valve responds to speed determined by the speed sensor and computer. The switching valve then allows or cuts off vacuum to the throttle positioner diaphragm. When speed is above approximately 16 MPH and throttle is suddenly closed for deceleration, the throttle positioner holds throttle plate at a slightly open position. When vehicle decelerates below 7 MPH, vacuum is cut off and throttle plate returns to normal idle position.

On Cressida (4M engine), the throttle positioner system is vacuum operated. Vacuum is routed through delay valve to the throttle positioner diaphragm. The delay action of the valve allows throttle plate to return slowly to normal idle position.