940 SE L4-2320cc 2.3L SOHC Turbo VIN 87 B230FT (1991)
Idle Control Valve: Description and Operation
Idle Air Valve
PURPOSE
The idle air valve controls constant idle speed. To set the correct air valve opening to achieve constant idle speed, the fuel injection control unit
uses information from the mass air flow sensor, A/C switch, throttle valve switch and the ignition control unit (RPM signal) to regulate the output
current to the idle air valve.
Idle Air Valve Operation
OPERATION
When the engine is running, the fuel injection control unit ensures that the idle valve is more or less open at all engine speeds to prevent the
development of unnecessarily high vacuum in the intake manifold during sudden deceleration.
If no current is supplied to the air valve, a spring sets the idle valve opening for an idle speed of 1050 ±50 RPM.
When the throttle valve switch idle contacts are closed during idling, the fuel injection control unit sends current to the idle air valve electric motor
to keep the idle speed at the correct level. This speed is preset in the fuel injection ECU and should remain constant regardless of engine load or
conditions.
If the throttle valve switch idle contacts are open (engine above idle speed), the fuel injection ECU does not send current. The idle air valve closes
to its default position, thus staying partially open so the vacuum in the intake manifold is reduced when the throttle valve suddenly closes.
