Idle Speed/Throttle Actuator - Mechanical: Description and Operation

Throttle Opening System (Throttle Opener Solenoid For A/C):

THROTTLE OPENING (FOR A/C)
When the engine speed is below the set speed (1,200 rpm), the ECU provides a ground to the throttle opener solenoid valve . When the air conditioner relay is turned on the throttle opener solenoid valve is energized to introduce intake manifold vacuum to the throttle opener. The throttle valve opens slightly preventing engine speed drop caused by air conditioner load.

Throttle Opening System:

IDLE-UP (FOR ELECTRICAL LOAD)
When the engine speed drops below the set speed (1,200 rpm), the ECU provides a ground to the idle-up solenoid valve. When the electrical switch is turned on for lighting (tail light switch) or the blower fan (fan only, heater or defroster), the idle-up solenoid valve is energized. This allows intake manifold vacuum to the idle-up Actuator to open the throttle valve slightly, preventing engine speed drop caused by electrical load. In addition, independently from the ECU, if the power steering oil pressure switch is activated (indicating a load) the idle-up control solenoid valve is energized to introduce intake manifold vacuum to the idle-up Actuator. The throttle valve opens slightly, preventing engine speed drop caused by power steering load.

DASH POT
The Idle-up actuator does secondary duty as a throttle closing Dash Pot under deceleration conditions. To accomplish this there is an adjustment screw (SAS 3) to limit the additional opening of the throttle. When the engine vacuum is higher than normal idle vacuum, the idle-up actuator pulls the throttle open the additional amount allowed by SAS 3.