I have a 2002 Audi A4 Quattro 3.0. I have a Vagcom USB cable and I am trying to diagnose the MAF sensor. I had a friend get some readings from an OBD2 scanner, which indicated that both precat O2 sensors (passenger side and driver side) had negative values. He said that it probably isn't the O2 sensors, since both of them are reading similar readings. He also said it is possibly the MAF sensor or a vacuum leak somewhere.
I have taken these readings from the MAF sensor. It appears that the "grams per second" is not going above 50, even when the engine is revving at 7000 rpm.
Does this indicate that the MAF is faulty? Is there anything else I can do to see if this really is the problem?
I have found this PDF:
http://www.ross-tech.net/vag-com/advertising/DiagnosingA_MAF_TechTip.pdf
Which indicates that this value should peak at about 160 g/s in a 200 horse power car. However, the altitude could be a factor in calculating this. I am located in Denver Colorado, roughly mile above sea level.
Any advice would be a massive help,
UPDATE: I wanted to add that the CEL's that came on are P0171 and P0174. I have tried spraying the MAF sensor with MAF Sensor cleaner that I got from Autozone, it didn't seem to make any difference, but I possibly didn't clean it properly? I took the sensor off an sprayed it all over, let it dry, and then popped it back in.
