A4 1.8T -2000 & MAF sensor
 

Hi,

MAF sesnsor problems are various. Typically there isn't any trouble
codes when MAF sensor goes bad and many other problems seems the same,
like: bad TB, O2 sensor, injectors, vacoom leaks in hoses etc....

In my case these symptoms came when I disconnected the battery -> ECU's
memory of TB adjustment and learned values of engine parameters where
cleared, the TB adjustment didn't seem to succeed. the idle was wery
poor and when driving the acceleration was awful. The solution was bad
MAF sensor. The ECU couldnt relearn the values because it didn't get any
reasonable values from MAF sensor. So why that happened after ECU was
restarted and before that the car was quite driveable... -I think reason
was that when the sensor was getting bad little by little the ECU
adjusted oneself to these wrong values and it could somehow manage it.
When I replaced the MAF sensor the car was almost better than new. Idle
was constant and acceleration good and smooth.

So the lesson was that if you hawe any kind of problems with idle and/or
the car is jerky but you don't get any trouble codes or check engine
light, CHECK THE MAF SENSOR. It's easy to notice. Just take of the MAF
sensor and look at it agens light, the surface of the sensor inside the
tube have to look like mirror when it's OK. If there is any dots like
fly's **** that MAF sensor is gone.

-K03