2002 Audi A4 car stalls when stopped in first gear or 1st g

I have an 02 A4 with 6 speed triptonic shifter
that gives me the option to drive an standard automatic or clutchless shifting.
When my car is in drive it seems that the engine stalls when it is at a full stop. Once I manage to take off the car up shifts perfectly. After driving for awhile on the highway the problem seems to go away but after the car sits for awhile and when ai take off again the problem will occur intermittenly, I already had a mechanic check out the ECM sensors which were fine. Except for the coolant sensor which seemed to have elivieated the problem temporarly. He even managed to replace the transmission fluid, o rings, and filter which was by far no easy task for an Audi as it is a sealed tranny with no plug or dipstick. So for now the ECM codes are coming back everything normal and fine but I'm still getting a stalling effect with the gear in drive or first while stopped. The only other thing I could think of is the engine idle may not be be right but again it does not appear to be that either.