Audi Repair: Audi A3 1.6 rough idle fault year 1999, mass air flow sensor, throttle position sensor

Question
I had my car in the garage for a rough idle problem. The mechanic changed the pre cat o2 lambda sensor, the mass air flow sensor, cleaned the throttle body and changed the crank sensor. The car is now idling too fast at 1200 revs. The mechanic is now saying that the ecu is faulty and it needs changing. I have already spent a lot of money and want a second opinion before spending more...

Answer
Was the check engine light on when you took the car in?  If not then your O2 sensor was probably OK...  Crank sensor will rarely cause bad idling, a mass airflow sensor can but mainly the idle control module and throttle position switch would be at the top of my list.   Check the connections to the idle control module, oh no wait, change mechanic first, then get new mechanic (or self) to check the connections to the idle control module and the module itself, get your old MAF back since that will be useful as a spare, and get a readout of any codes that may exist on the computer.  Also have the throttle position sensor (TPS) checked, and let me know what you find.  Cheers,  Jan