Hi all I've got an audi a3 1.6 2003 and the last two days I've had an issue where I start it in the morning and it's revining past 1 thousand revs then back again the engine is jurking, if I leave it for 10 minutes then try again it then starts up fine and white smoke comes out the exhaust I have took it to a a garage they've checked the oil etc and said they can't find the issue and nothing is showing error wise any help would be great