1979 Models

Warm engine to normal operating temperature. Check and adjust idle speed if required. Allow engine to idle and note that throttle positioner diaphragm releases throttle.
On Corolla and Cressida, disconnect vacuum hose from throttle positioner diaphragm. Throttle positioner should now be activated.
On Celica, Corona and Pickup, connect vacuum hose going to throttle positioner directly to intake manifold vacuum. Throttle positioner should now be activated.
On all models, with throttle positioner activated, check engine speed. Engine speed should be as specified in THROTTLE POSITIONER SET SPEED table. If speed is not as specified, turn throttle positioner adjusting screw. On Cressida, turn throttle positioner diaphragm.

THROTTLE POSITIONER SET SPEED