Well, you may not like the answer, but one very common issue that causes this is a failing torque converter lock-up clutch.
There is an Audi TSB on it. 32 12 03 2028608/1 February 3, 2012
A4, A4 Avant, A4 Cabriolet 2004 - 2009 - all with 09L transmission.
Basically it says to use the factory scan tool to watch the trans TCC and verify that it is/is not going into lock-up.
On a good scan tool the TCC data should show "off" and "on" showing the state of the clutch.
If it reads "CNTRL" constantly the TCM it trying to command the TCC to full on or off but it is not occurring. The repair is a new converter.
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Friday, January 20th, 2017 AT 2:01 PM