[s-cars] Tat..Tat Noise in Engine

[Max Hoepli]

I have a MC engine in Type 44 Quattro, with turbo charger  with 285,000 km. when idling it makes a tat...tat....tat......tat.......tat...noise from top part of engine. When inside of car noise is not heard. Engine never overheats, starts immediately. Sometimes there is white smoke coming out of exhaust just after starting. I alternately fill tank with RON 89 and 91. What could problem be?...if any? Gasoline may be issue. Could Rislone additive help?


Max