Checking and replacing the additional air damper (BMW 3 Series E30)

When warming up, the engine requires more air-fuel mixture than is determined by the position of the throttle valve. To increase the supply of the mixture, a channel bypassing the throttle valve is opened using an additional air valve. On a warmed up engine, the cross-section of the additional channel must be closed.

A faulty auxiliary air damper may cause the engine to stall or run rough during warm-up or have unregulated idle speed.

Examination

Note: The engine must be cold when checking.

Disconnect the auxiliary air damper connector, (lower right arrow).

Connect a voltmeter to both contacts of the connector.

Start the engine. The voltmeter should show battery voltage, otherwise find and fix the wire break.

Reconnect the connector.

Start the engine and let it run in idle mode.

Disconnect the hose from the additional air damper, after which the engine idle speed should drop.

Warm up the engine and disconnect the hose again. The engine speed should not change. Otherwise, replace the additional air damper.

Replacement

Disconnect the connector.

Loosen the clamps and disconnect the hoses.

Loosen the 2 mounting bolts and remove the additional air damper.





The rotary damper is visible through the cover. When hot, the damper should be completely closed. When cold, there should be a gap. When warming up the additional air damper, apply battery voltage to the connector contacts using auxiliary wires.

Insert and screw in the additional air damper.

Connect the hoses and secure them with clamps.

Caution: Ensure hoses are securely installed.

Connect the connector.