Sidekick Sport 2D JX 4WD L4-1.8L (1998)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
IDLE AIR CONTROL SYSTEM
This system controls the bypass air flow by means of ECM and idle air control valve (IAC valve) for the following four purposes.
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To keep the engine idle speed as specified at all time.
The engine idle speed can vary due to following reasons.
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Load applied to engine (when electric load is applied, automatic transmission is shifted to "R", "D", "2" or "L" range, A/C is turned ON, etc.)
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Variation in atmospheric pressure
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Change in engine itself with passage of time
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Other factors causing idle speed to change
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To improve starting performance of engine
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To compensate air/fuel mixture ratio when decelerating (Dash-pot effect)
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To improve driveability when while engine is warmed up.
Operation
IAC valve opens the bypass passage when it is turned ON by ECM and closes when turned OFF.
ECM detects the engine condition by using signals from various sensors and switches and while repeating ON and OFF cycle of IAC valve at a
certain rate (320 times a second), it controls bypass air flow (IAC valve opening) by increasing and decreasing its ON time within a cycle.
When the vehicle is at a stop, the throttle valve is at the idle position and the engine is running, the engine speed is kept at a specified idle speed.
