hi i have just bought an a6 2.5tdi 180 and within the last week it has started to produce a lumpy spot when in 6th gear.

it happens when i am cruising at constant speed on the motorway and then try to accelerate gently to do an overtake, the car loses pwer momentarily then picks up and is fine again. when this happens the revs strangely do not rise or fall. this has happened at different road and engine speeds each time. it is a similar feeling as if the clutch has been rapidly pushed in and released again.

can anyone help please?