[boschmann]

I have come across more of them that are out of calibration than just quit. Unfortunately what typically happens is they start giving erroneous readings which are within the accepable parameters, it is just calculating the air flow wrong. The result is an incorrect air/fuel ratio and the computer starts having trouble making the engine run correctly, but doesn't know what the problem is. The only way to find this is to use a generic scanner to look at the computer datastream at the fuel trim values and O2 readings or a VAG scanner to look at certain measuring blocks. Some people have had luck cleaning the sensor in rubbing alcohol (at least 90%). I have tried this but have not been successful yet, if you try it be very careful as the sensor is fragile (do not touch the center wire with anything, only soak it).