Idle Air Control Valve

GENERAL INFORMATION

Idle Air Control Valve

1. CONTACT PINS.

2. BALL BEARING.

3. STATOR.

4. ROTOR.

5. SPRING.

6. IAC VALVE CLOSING ELEMENT.

7. DRIVE SCREW.

IAC Valve Closing Element

The ECM controls engine idle operation using the idle air control (IAC) valve installed in the throttle body. The IAC valve regulates engine idle speed by metering airflow through a bypass passage parallel to the throttle valve.

The IAC valve regulates engine idle speed by metering airflow through a bypass passage parallel to the throttle valve.

The IAC stepper motor is controlled by pulses from the ECM. With each control pulse, the motor rotor rotates through a set angle, moving the valve closing element relative to the seat via a screw mechanism.

The IAC stepper motor is controlled by pulses from the ECM. With each control pulse, the motor rotor rotates through a set angle.

Changing the flow area between the closing element and the seat regulates airflow through the bypass passage.

Changing the flow area between the closing element and the seat regulates airflow through the bypass passage.

Using the IAC valve, the ECM maintains the target idle speed. Target values are stored in ECM memory as a function of engine coolant temperature, the Park/Neutral switch signal, vehicle speed, battery voltage, and air conditioning system pressure.

Target values are stored in ECM memory as a function of engine coolant temperature, the Park/Neutral switch signal, vehicle speed, battery voltage, and air conditioning system pressure.

The ECM determines the IAC valve closing element position based on the required idle speed of a warmed-up engine for various operating conditions (for example, when the automatic transmission selector is in Park or Drive, the air conditioner is on or off, etc.).

The ECM determines the IAC valve closing element position based on the required idle speed of a warmed-up engine for various operating conditions (for example, when the automatic transmission selector is in Park or Drive, the air conditioner is on or off, etc.).

Idle speed values are stored in ROM, where the data is retained after the ignition is turned off.

Idle speed values are stored in ROM, where the data is retained after the ignition is turned off.

This data is the starting point for the ECM when calculating the current IAC valve position.

This algorithm eliminates the dependence of idle speed on various random and systematic factors, such as engine wear or random deviations of the throttle valve from its nominal position with the accelerator pedal released.

The ECM automatically maintains idle speed at the required level.

However, when ECM power is disconnected, normal engine idle operation may be disrupted. As a result, when starting the engine, it may be necessary to partially depress the accelerator pedal until the ECM begins controlling engine idle automatically.

As a result, when starting the engine, it may be necessary to partially depress the accelerator pedal until the ECM begins controlling engine idle automatically.

Engine idle speed depends on the airflow entering the intake manifold. This total airflow consists of airflow through the IAC valve, airflow past the closed throttle valve, and a small airflow through the vacuum hoses connecting the intake manifold to various vacuum devices.

Engine idle speed depends on the airflow entering the intake manifold.

This total airflow consists of airflow through the IAC valve, airflow past the closed throttle valve, and a small airflow through the vacuum hoses connecting the intake manifold to various vacuum devices.

Initial throttle valve position when

with the accelerator pedal released is adjusted and sealed with the limiter screw at the factory. This throttle position provides sufficient air flow in the intake manifold for the IAC valve to be set to the required discrete position during automatic speed adjustment. Note that for this engine, the initial throttle position cannot be considered the position corresponding to minimum idle speed. The idle limiter screw head is covered by a cap. WARNING.

Do not remove the protective cap of the limiter screw and do not perform

adjustment. Incorrect adjustment may damage the IAC valve or

throttle body.

The ECU updates the calibration of the idle air control (IAC) valve position after

each ignition switch-on and when vehicle speed exceeds 48 km/h under moderate acceleration. The calibration procedure includes full retraction

records the initial "zero" position of the valve, from which

the count of discrete steps is set. If after the described procedure

calibration the ECU is unable to maintain the nominal idle speed within

of the ECU calibration is able to maintain the nominal idle speed within the

specified range of discrete IAC valve positions. The obtained calibration is stored until the next ignition switch-off and switch-on, engine start and acceleration above 48 km/h. Otherwise

the nominal engine idle speed is maintained within the specified range of IAC valve discrete positions.

Throttle Position Sensor (TPS)