I have a 1.9 TDI A6 which has started to fail to start when warm. It is most apprent after being driven hard and is hence hot, it doesnt seem to fire properly and judders. When cooled down a bit it starts fine and drives fine. Could it be dirty injectors - which cleaner addertive is best? Could it be a temp senser - temp gauge looks ok? Does the ECU/management system have a different temp senser?

Please help - its driving me mad.

 

vapor locking possibly? next time it does it, take the fuel cap off and listen as you do it. if it makes a noise like a new bottle of pop being opened, it might not be venting properly and causing the system to vapor lock, in which case it might be as simple as just replacing your fuel cap.

 

Thanks, I tried removing the cap but no change also have changed the coolant temp sensor also to no effect. I only does it when its very warm and it does seem like fuel starvation - is there anywhere in the system that could vapour lock when hot?