Accord L4-2.4L (2005)
Idle Speed: Description and Operation
Idle Control System
The engine idle speed is controlled by the idle air control (IAC) valve:
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After the engine starts, the IAC valve opens for a certain amount of time. The amount of air is increased to raise the idle speed.
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When the engine coolant temperature is low, the IAC valve is opened to obtain the proper fast idle speed. The amount of bypassed air is controlled
in relation to engine coolant temperature.
When the engine is cold, the A/C compressor is on, the transmission is in gear, the brake pedal is pressed, the power steering load is high, or the
alternator is charging, the ECM/PCM controls current to the idle air control (IAC) valve to maintain the correct idle speed. Refer to the System Diagram
to see the functional layout of the system.
Brake Pedal Position Switch
The brake pedal position switch signals the ECM/PCM when the brake pedal is pressed.
Idle Air Control (IAC) Valve
To maintain proper idle speed, the IAC valve changes the amount of air bypassing the throttle body in response to an electrical signal from the
ECM/PCM.
Power Steering Pressure (PSP) Switch
The PSP switch signals the ECM/PCM when the power steering load is high.