Civic L4-1668cc 1.7L SOHC MFI (2003)
Idle Speed: Description and Operation
Idle Control System
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.
Idle Control System Diagram
The idle speed of the engine is controlled by the idle air control (IAC) valve:
-
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.
-
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 thus
controlled in relation to engine coolant temperature.