Esteem L4-1590cc 1.6L SOHC 0 MFI 16V (1995)
Idle Air Control (IAC) Valve: Description and Operation
This system controls the bypass air flow by means of ECM and Idle Air Control (IAC) for the following four purposes.
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To keep the engine idle speed as specified at all times. 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
Opening of IAC valve is controlled according to IAC valve opening signal (A3 ON) and closing signal (A16 ON) sent from ECM. ECM detects
the engine condition by using the signals from various sensors and switches and controls the bypass air flow by changing the ratio between the
time (To) within a cycle during which electricity flows through the IAC valve coil (open) (i.e., A3 ON time = IAC valve moves in its opening
direction) and the time (To) during which electricity flows through the lac valve coil (close) (i.e., A16 ON time = IAC valve moves in its closing
direction). 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
