Air distribution valve
Cars from model year 1999-2000 have an air distribution valve. The air distribution valve supplies the injectors with air. This results in better volumetric efficiency, more effective combustion and therefore cleaner exhaust emissions. The valve is also used for idle air trim but is also slightly open at higher engine speeds.
The valve is directly mounted on the inlet hose for the electronic throttle module (ETM). The valve is connected to a hose which supplies air to the air-shrouded injectors via a distribution pipe.
The valve has its own ignition driver stage and solenoid and is supplied with 12V. The valve is controlled steplessly by the Engine Control Module (ECM) using a variable pulse ratio (duty-cycle) which opens or closes a shutter in the valve.
The valve works primarily during cold starts and when idling, to minimize the release of carbon dioxide and hydro-carbons whist maintaining performance and driveability. This is partly because the size of fuel drops is smaller with fuel mixed with air and does not adhere as easily to the walls of the intake manifold when they are cold and damp. This also reduces fuel consumption when cold starting and cuts the warm up time for both the engine and the three-way catalytic converter (TWC).
The total calculated volume of air to be released into the combustion chamber is distributed between both the Electronic Throttle Module (ETM) and the air distribution valve. The input signals to the Engine Control Module (ECM) which affect the operation of the air distribution valve are: the position of the throttle, engine speed (RPM)/position sensor, engine coolant temperature (ECT) sensor, ambient air pressure and ambient air temperature.
The air distribution valve can be diagnosed by the Engine control module (ECM) and can be activated using VIDA.