Audi A4 - engine warning light - X reg audi

some 6 dignostics all show same result that the fuel air mix is lean. On correction car runs for approx 20 miles with no warning light and then it comes on again. Both relevant Bosch sensors have been replaced and the catalytic converter cleaned. No difference to petrol consumption and the garage confirms no adverse effect on performance. Have driven some 2000 miles with this apparent fault. Can I just ignore it and could it cause a problem with MOT.

Audi A4 - engine warning light - A3 A4

Had similar on my A3 it turned out to be the temperature sensor, which can give a myriad of symptoms. Its cheap enough an easy to replace.

Edited by A3 A4 on 28/04/2013 at 11:36

Audi A4 - engine warning light - elekie&a/c doctor

There are no specific sensors that relate to a lean mixture.All the sensors on the engine are used to maintain a correct air fuel ratio depending on engine load/speed etc.I would guess you mean the lambda sensors have been replaced,probably for no reason.I would take a look at the air intake and breather,and vacuum pipes circuits.Any leak here will cause a lean mixture fault to be logged.Take it to a garage that have a smoke machine.This should identify any problem areas.hth


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