Celica & Pickup

With engine cold, connect a vacuum gauge to distributor main advance diaphragm hose. Check that coolant temperature is below 86°F (30°C). Start engine. Vacuum gauge should indicate zero regardless of whether throttle valve is open or closed.
Warm up engine to normal operating temperature. Check that vacuum gauge changes quickly when throttle valve is opened and closed. Stop engine. Remove vacuum gauge and reconnect hose to distributor.
Remove distributor cap and rotor. Apply vacuum to diaphragms checking that vacuum advancer moves in accordance with vacuum. Reinstall rotor and cap. If system performed as described, testing is complete. If not, check individual components as necessary.

Fig 1: Spark Control System (Celica & Pickup)