My 2003 A6 1.9TDI has started to give me problems starting when warm. It starts fine when cold runs fine and pulls great but when warm it sometimes fails to 'catch' first time and judders quite violently. After 3 or 4 attempts and keeping it turned over it will eventually start but it doesn’t sound good - it gives a loud 'knocking' as if misfiring. it doesn’t do it all the time and I think it must be fuel related. Any clues anyone before I go down that very expensive dealer path.

Thanks

Paul