Idle speed and CO content — check (Audi 80 B4)

Idle speed adjustment is not necessary on cars with the Digifant fuel system, because this system is "self-learning". This means that the electronic control unit itself adjusts the engine speed at idle speed if necessary. And only when there are sufficiently justified suspicions of an imbalance in the idle speed, the so-called main adjustment is performed. It is performed not by turning the adjusting screws, but with the help of the already mentioned VAG 1551 device, and only after the data storage device has been interrogated about the malfunctions or failures that have occurred in operation. As for the number of revolutions and CO content, the following values are the control ones:

• idle speed 820±50 rpm
• cO content in exhaust gases 0.6-1.0%

These data are valid provided that during the test the engine was warmed up to operating temperature, all consumers of the on-board network were disconnected, and the ignition timing was set correctly.

If the data obtained during the check does not match the specified values, check the condition of the low-pressure supply hoses, the fuel vapor recovery system solenoid valve, and also interrogate the data accumulator for system malfunctions that have occurred.

[The original text is available on the website: AUDImanual.ru]