Structure and function of the idle speed control valve

The idle control valve is located on the throttle body and closes the throttle almost completely when idling. Types of idle control valves include mechanical, solenoid valve, rotary valve and stepper motor. There is a wide variety because of their different principles and structures. When the engine idle load increases, the ECU will control the idle control valve to increase the air intake, thus increasing the idle speed and preventing the engine from being unstable or stalling; when the engine idle load decreases, the ECU will control the idle control valve to decrease the air intake, thus decreasing the idle speed and preventing the idle speed from being too high. The idle speed control valve is installed on the vent hole next to the throttle. According to the ignition signal, the idle speed controller will make the idle speed control valve act in time to increase the engine speed when the engine speed is lower than 750 rpm, and stop the action when the engine speed exceeds 1050 rpm. In vehicles equipped with an air conditioning system, this control valve is also known as the idle acceleration valve. When the air-conditioning compressor operates, generating an engine load that reduces the engine idle speed, the idle speed control valve will act accordingly to keep the idle speed stable. The idle control valve is used to adjust the idle speed when the engine's operating parameters deviate from normal, by controlling the amount of air bypassing the throttle body. After the engine is started, the idle control valve will open for a period of time and the intake air volume will increase, increasing the engine idle speed by about 150 rpm-300 rpm. When the engine coolant temperature is low, the idle control valve opens to obtain a proper fast idle speed. Depending on the coolant temperature, the computer controls the position of the idle control valve plunger by changing the strength of the signal transmitted to the idle control valve. A solenoid idle control valve is actually a solenoid coil, and the ECU controls the current to the coil and the opening of the control valve through a duty cycle. The rotary valve idle control valve is a type of motor-driven idle control valve. The stepper motor idle control valve is the most widely used, and it adjusts the idle speed by controlling the amount of air bypassing the throttle to achieve the desired idle speed. There is also a paraffin idle control valve, which mainly utilizes the principle of paraffin wax to open at low temperatures to increase the engine's idle speed, and then lower the spool to stabilize the idle speed as the temperature rises. Idle control valve is also equipped with idle speed adjustment screw, used to adjust the idle speed.