Exhaust Emissions System - Throttle Opener System: Operation
The throttle opener system is designed to prevent misfire during deceleration by causing the throttle valve to remain slightly open allowing better combustion. The control valve is set to allow the passage of vacuum to the throttle diaphragm when the intake manifold vacuum is equal to or greater than the control valve preset vacuum during deceleration.
Under normal operating conditions, the intake manifold vacuum is less than the preset vacuum of the control valve and the valve is not actuated. However, a sudden change in vacuum (throttle suddenly closed) will actuate the throttle opener for the required time interval. The throttle opener then returns to the normal position as the vacuum remaining in the throttle opener and control valve is returned to atmospheric pressure through the orifice in the control valve.