I was under the impression that if the lambda readout fluctuates at all, there is no fault in the system, and that only when it is static at 10% do you have a fault in the system ... in this case the air flow potentiometer.

Did you warm up the engine to operating temp before taking a reading? (80ºc)

Someone please correct me if I'm wrong.

Good Luck

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi