Impreza Outback Sport AWD F4-2.5L SOHC (2002)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control Solenoid Valve
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The idle air control solenoid valve is located in the throttle body and regulates the amount of intake air that flows bypassing the throttle valve into
the intake manifold during engine idling. It is activated by a signal from the ECM in order to maintain the engine idling speed at a target speed.
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The idle air control solenoid valve is a stepping motor type solenoid-actuated valve which consists of coils, a shaft, a permanent magnet, a spring
and a housing. The housing is an integral part of the throttle body.
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The stepping motor consists of two paired coils, the coils of each pair being arranged face to face with a shaft in between.
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The shaft has a screw at the end around which the permanent magnets are arranged.
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As current flows in the form of pulses through the paired coils sequentially while alternating the polarity, the N and S poles of the permanent
magnets around the shaft are repelled by the same poles of the magnetism generated by the coils. This causes a nut externally fixed to the magnets
and internally engaging with the screw of the shaft to turn.
The shaft then goes upward or downward.
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This upward and downward motions of the shaft open or close the valve port, adjusting the amount of bypass air.
