Checking the additional air valve (engines 90, 102, 112 hp; designations JM, DZ, ABB) (Audi 80 B3)

During warm-up, a larger amount of fuel-air mixture is supplied to the engine than corresponds to the nominal adjustment of the throttle valve. To do this, additional air is supplied through the valve bypassing the throttle valve. When warmed up, the additional hole is closed.

If the additional air valve is faulty, the following problems may occur: the engine stalls or idles erratically during warm-up, or the idle speed is incorrect.

Examination

Note: The engine must be cold when checking. Coolant temperature below +30°C.

Caution: Immediately before checking the valve, the ignition can only be turned on with the auxiliary air valve plug disconnected, otherwise the air valve will heat up, which will lead to incorrect test results.

Disconnect the high voltage wire - terminal 4 - from the distributor (central cable) and short it to ground; if necessary, use an auxiliary wire of the same cross-section.

Disconnect the auxiliary air valve plug

Connect a voltmeter between the plug contacts.

Turn on the starter briefly. The voltmeter should show battery voltage, otherwise check the electrical wires for breakage.

Connect the high voltage cable to the ignition distributor.

Connect the tachometer according to the instructions.

Start the engine and let it idle.

Clamp the hose to the additional air valve with pliers, the idle speed should decrease.

Connect the plug to the additional air valve.