The Extra Air Valve is a very robust component of the Rover SD1 Efi System and because of its simplicity should rarely fail mechanically unless there has been interference of the internal components with a screwdriver or similar intrusion.

It is however susceptible to electrical problems, as is any coil heating device but is much more likely to suffer from connection problems This is particularly so, because the electrical socket is inaccessible when mounted on the Rover SD1 manifold and the plug can become dislodged or the connections can become corroded whilst its inaccessibility prevents easy fault diagnosis.

The Extra Air Valve's robustness also means it rarely fails with regard to air leaks within the component itself but the same cannot be said of the rubber hoses connecting it to the air rail and plenum chamber respectively.

A fundamental feature of the Rover SD1 Efi System is that, providing the volume of air entering the engine is accurately measured by the Air Flow Meter, the Electronic Control Unit will always calculate the correct amount of fuel needed to maintain the required air/fuel (stoichiometric) ratio.

When the engine starts from cold the Electronic Control Unit also has to overcome a temporary increase in friction caused by the viscosity of cold oil. There are no sensors measuring this but if ignored it will swamp normal idle speed and cause it to stall.

To prevent such happening, the idle speed of the engine is artificially raised by introducing more metered air to the engine via the Extra Air Valve.

This article explains the nature and operation of the Extra Air Valve and how to carry out approprate tests.

The contents of this article are listed above. Read or download it in PDF format here (91kb)

Please advise of errors and omissions.