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Descripton and Function of Aux Air Valve, Series III XJ6

Descripton and Function of Aux Air Valve, Series III XJ6

Paul Spitzer

The auxiliary air valve is exactly what it says it is. With the FI system the throttle butterfly can be thought of as the pedal controlled main air valve. The AAV when cold automatically opens a small second air passage or throttle if you will to elevate the cold idle speed. The AAV passage gradually closes off from the warming water rail plus an electrical element. Air available to the AAV is monitored by the AFM the same as air to the main throttle plate.

Problems can be as Art mentioned - if stuck open the idle can't be adjusted. Stuck closed the cold idle will be unsatisfactory. On the XJ6 cars the hose from the AAV to the underside of the intake manifold is often forgotten and can have failed. You won't see it unless you get under the car. The AAV is simple to check. Pop off the hose from the throttle block to the AAV when cold - you should see a hole or passage directly through the device. A portion of the blanking plate may be visible but the passage should be quite open and obvious. Put the hose back on and run the car up to temp, shut down, and pull the hose back off. The passageway should now be completely blanked off. The electrical tests can be done as described in the manual but IMHO if the device won't function with the temp provided by the water rail closing the passageway it's time for a new one. If the piggy is in need of more pennies before purchase can be made plugging the hose before the device will mean your foot becomes the cold speed controller. Good Luck, Paul Spitzer


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