Mass Airflow Sensor

It measures the amount of air going into the engine.

Determines the amount of air through the air filter to the air intake mainfold. Does this by a sensor in the air flow path by moving per the amount of air going through that path, and, delivering a (electrical) current in reflection of that sensor movement. Seldom breaks or degrades, leave it alone.

also has internal air temperature sensor.

Thanks for the answers.

Although the earlier a4-platform VWs had one that did have a higher probability of failing.

Same with the A3's. AND it was expensive as hell. The worst thing you can do to destroy the MAF is put an aftermarket cold air intake on it with an over oiled air filter. The oil coats the MAF which then burns off and leaves a deposit that screws up the readings.

Chilton claims the mass airfllow sensor can cause running problems if it's failing: stalling and idle problems

yep I have yet to see a bad one yet, but I have heard of them. ;-)

Had our 2000 Jetta in the shop three times with a stalling and idle problem. They changed out the MAF Sensor twice, only to have the issue raise it's head again. On the third try, they found the electrical plug to the sensor to be faulty and changed it out. No problems since.

Ray in Texas

My MAF was causing stalling and idling problems on my 97 Jetta. I used the alcohol cleaning scheme that is on vwvortex about 50,000 miles ago and haven't had a problem since then. At that time, VW or any other supplier wanted over $500 for a new one while other years' MAF only cost around $50. I see the price is coming down now. I don't know what makes mine so special.