Idle air control valve (IAC)
| Idle air control valve (IAC) |
IAC = Idle Air Control
When the accelerator pedal is unmoved and the throttle closed, the fuel mixture gets its air only via the IAC- valve.
The control module controls the angle of opening in the valve so as to keep the idling speed constant. This means for example that the valve opens when connecting A/C or when selecting DRIVE, so as to compensate the idling speed, which would otherwise decrease.
The IAC valve, which has 2 coils, receives its voltage from the main relay.
The signal from the control module pin 4 opens the valve by activating one of the coils and closes the valve by activating the second coil from the control module pin 22.
The interplay between these two signals guides the opening in the IAC valve, so that the idling speed is kept at the right level when the car speed is lower than 3 km/h.
When the following are engaged the increase in the air flow through the valve will be:
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DRIVE position approx. 1.1 gram/s
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A/C compressor approx. 1.4 gram/s
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Radiator fan approx. 0.4 gram/s
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The signals are PWM signals at 100 Hz which at idling speed measure:
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Pin 4 approx. 2-5 volts
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Pin 22 approx. 7-10 volts
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If an open circuit occurs the opening in the valve is set by a spring so that the idling speed will be at least 1000 rpm.
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