Subaru Air Conditioning Systems
Bypass Adjusting Screw (ECVT)
TBI (IAC)
MFI/TBI FICD Operation
Fast Idle Control Device (A/C Idle Air Control)
On manual transaxle equipped Justy vehicles, the FICD is incorporated in the
On ECVT equipped carbureted vehicles an air/fuel bypass control system performs the FICD function. The ECVT air bypass control system consists of an air bypass valve, an adjusting screw, and an air bypass solenoid. The system is designed to increase idle speed whenever the A/C relay is activated by supplying additional air/fuel into the intake manifold.
Bypass air enters through the air horn on the secondary side.
The airflow is regulated by an adjusting screw. When the bypass valve opens, bypass air/fuel enters the manifold below the secondary throttle plate.
When the adjusting screw is turned clockwise, bypass air/fuel is reduced and the idle speed is lowered. When the adjusting screw is turned counter clockwise, bypass air/fuel is increased and the idle speed is increased.
Note: Always refer to the appropriate Justy model year Subaru Service Manual sections
TBI system equipped Loyale vehicles control the FICD function through the ECM, the idle air control valve (IAC), and the A/C switch. The air conditioning ON/OFF switch is an input to the ECM. The ECM operates the idle air control valve (IAC) to adjust the idle speed to compensate for the increased compressor load. No adjustment is required.
On all model year Loyale and XT MFI vehicles, an FICD solenoid incorporated in the throttle body provides the increase in idle speed. The throttle body includes an adjustment screw for adjusting the FICD specification.
All Legacy, SVX and XT6 vehicles use an idle air control valve to provide the FICD function. The valve opens a port during A/C operation which admits additional air into the induction system.
Impreza vehicles use a solenoid which initially compensates for the increased compressor load when the air conditioning system is switched ON. The A/C IAC then compensates to maintain engine speed at target RPM.
Note: The Impreza FICD solenoid is set at the factory and should not require adjustment. Any changes to the adjustment can affect driveability and vehicle emissions during cold engine operation.
Justy MFI vehicles increase idle speed by admitting additional air into the air collector assembly through the FICD solenoid which is opened by a signal from the MFI control unit.
End Wrench
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A/C Idle Air Systems | Impreza FICD |
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