I have had this car at the dealer 3 times with this complaint, and when the car bucks, you can see the rpm drop even though pressure is constant on fuel pedal. I have told them it's something with the throttle position sensor, but they disagree. No engine fault comes up so they won't do anything even though they have experienced the bucking as well. What now?
the car bucks when engine is cool and/or air is humid on 2009 Volkswagen Jetta
Your car is under warentee, I would call VW North America or demand that the car be fixed or an appointment made to see the regional VW representative. The VW scan tool should be able to monitor and watch live sensor information from the airflow meter, throttle position sensor and many more key inputs. Just because there is no stored code or pending code stored doesn't mean the problem can not be found. Even good aftermarket scan tools can read VW sensors on slightly older VW's.