Vacuum Throttle Positioner

Fig. 16 TQ vacuum throttle positioner adjustment:

1. Start engine and allow to idle in Neutral position, then accelerate engine to a speed above 2000 RPM.
2. Ensure that vacuum positioner unit operates and can withstand a hand applied load in the operating position. If operation is satisfactory proceed to step 3, if not satisfactory proceed as follows:
a. Check all wiring harness and hose connections in system.
b. Check vacuum actuator by applying vacuum from an external source, Fig. 16. If actuator does not operate, replace. If actuator does operate, pinch off supply hose and observe actuator. Actuator should remain in operating position for one minute or more to be satisfactory.
c. Check vacuum solenoid by applying vacuum from an external source to manifold supply hose connection on solenoid valve. Disconnect wiring harness electrical connector from solenoid and ground one terminal of solenoid. Connect 12 volts to other terminal and observe vacuum actuator operation. If actuator does not cycle as 12 volts are applied, replace solenoid. If operation is normal, replace speed switch.
3. Reduce engine speed to 2000 RPM.
4. Loosen positioner adjustment locknut, then completely rotate vacuum positioner assembly until positioner just contacts throttle lever, Fig. 16.
5. Release throttle, then slowly adjust positioner to decrease engine speed until a sudden drop of 1000 RPM or more occurs.
6. Continue adjusting positioner an additional 1/4 turn, then tighten lock nut.
7. Accelerate engine to approximately 2300 RPM and release throttle. Engine should return to normal idle.