Outback [Legacy] AWD F4-2.5L DOHC (1996)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control
IDLE AIR CONTROL
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The ECM activates the idle air control solenoid valve in advance to control the amount of by-pass air flowing through the throttle valve in relation
to signals emitted from the crankshaft position sensor, camshaft position sensor, engine coolant temperature sensor and A/C switch, so that the
proper idle speed specified for each engine load is achieved.
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The idle air control solenoid valve is a rotary type and operates by duty cycle. For this reason, the by-pass air flow is regulated by controlling the
duty ratio.
The relationship between the duty ratio and by-pass air flow is as follows:
Duty ratio (high) -> Increases by-pass air flow.
By-pass air control features the following advantages:
1. Compensation for engine speed under A/C (air conditioning) system and electrical loads.
2. Increase in idle speed during early stage of warm up period.
3. A dashpot function during the time the throttle valve is quickly closed.
4. Prevention of engine speed variations over time.
