Impreza L Sport Wagon F4-2.2L SOHC (1999)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Description
California Only
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The idle air control solenoid valve is incorporated in the throttle body and regulates the amount of intake air which bypasses the throttle valve built
into the throttle body. It is activated by a signal sent from the ECM to mainly maintain engine idle speed to the target engine speed.
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The idle air control solenoid valve is a rotary valve solenoid type which consists of a coil, rotary valve, spring and housing. The housing is integral
with the throttle body and is provided with the opening area of bypass air port which is changed by the rotary valve.
Except California
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The idle air control solenoid valve is incorporated in the throttle body and regulates the amount of intake air which bypasses the throttle valve built
into the throttle body. It is activated by a signal sent from the ECM to mainly maintain engine idle speed to the target engine speed.
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The idle air control solenoid valve is a "stepping motor" type solenoid valve which consists of coils, shaft, permanent magnet, spring and housing.
The housing is integral with the throttle body.
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In stepping motor type air control solenoid valve, current flows sequentially through a series of paired coils which are arranged face to face with
the shaft between, while alternating the polarity for each pair of coils.
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The shaft is provided with threads at the rear end around which permanent magnets are arranged.
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As current flows through a series of paired coils sequentially while alternating the polarity, the N and S poles of the permanent magnets of the
shaft end are repelled by the same poles of the coils, which causes the shaft to turn.
The shaft, provided with threads, goes upward or downward like a screw when it is turned.
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This upward and downward motions of the shaft open or close the valve port, adjusting the amount of bypass air.
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The shaft changes its turning direction when the current flowing direction is reversed.
