Occasionally, but not all the time, the engine gives a single 'clang' or 'knocking' sound when the engine is turning over. I've been telling myseld it's just a start-up quirk since it doesn't happen often and the car runs fine. Since it's infrequent, I can't take to Volvo because I know it won't do it then. But for know or until it worsens, does anyone know about this? S60 AWD, 2002.<P>Thanks all.