Griff75

Hi, I brought recently an Audi A4 S Line Quattro Convertible 3L Diesel 2006 and when I am sat stationary with the engine ticking over the car produces a blue/grey smoke out of the exhaust. This does not effect the power or performance. This never happens when I am travelling at any speed only when I come to stand still in a traffic jam or moving at very slow speed in a traffic jam. I had had various test done but nothing has been found. Does anyone have any ideas please. Thanks you