I have been running my 2002 A4 B6 quattro estate for 10000 miles with no problems since my last major service. (The total mileage is now 106000 miles.)

A few weeks ago, whilst decelerating with my foot off the pedal, going downhill for instance, the engine started taking a wee dive forward two or three times as if I had blipped the accelerator. Going downhill the car is usually in second gear so the revs are reasonably high. (Static tickover is c.900rpm.)

Can anyone suggest what may be the problem?