Last week my year old A 1 1.6 TDI was running a bit lumpy on start up but eventually got going. I drove for about 25 miles before the car could not idle at traffic lights and stalled. I could not get thye car restarted and so called out Audi Assist. They checked the car and also were stumped as there were no fault codes and the system fuel pressure indicated no problems on diagnostics. The car was towed to Lomond Audi in Glasgow who carried out further investigations for a couple of days. They said that the car appeared all OK and even the EGR was fine. They were stumped and contacted the technical experts at Audi Technical advice centre. They decided to change all Injectors!!!!! Not sure why but a stab in the dark maybe. The car did start for them but is running really rough!!! They are now carrying out further tests to see if they can nail the fault. Any suggestions would be welcome as even Audi themselves are baffled by it.