Immediate stall when starting - knocking sound

[Noxidretep]

I hate it when something isn't obviously broken...

I have a 2010 A3 Sline 140 2l diesel, just ticked over 100k miles.

it has recently started stalling immediately after starting - almost like the engine is about to start and then dies. Only noticed this happened on a warm engine once I've been driving a while.



secondly - today it was doing its funny not starting thing so I videoed it - once it started it began making this loud distinct knocking sound, which stopped/quietened when the clutch pedal was depressed or I increased revs.

not sure if the 2 Are coming hand in hand or what - really frustrating me!

-any help would be massively appreciated!

video below:
Stall on start then knocking sound - YouTube

[alankru]

That's a familiar symptom to me! The "stalling" issue is exactly as mine was (only I usually got something on the rev counter as well) and it was due to the starter motor. It is common unfortunately - replace only with a genuine vag part. You can read more here (I've linked to further threads in that topic to explain diagnosis): Audi a3 tdi

The knocking issue may be related as if I recall correctly from other member's feedback, it can run a bit rough afterwards - whilst yours is particularly bad though. Is it only like that when you have the starting issue? If so, I would suggest that you first start with getting the starter motor diagnosed/replaced and see how it is. Oil ok etc?

[Noxidretep]

Apologies for the late reply -
Story is soon after car went into limp mode, error codes Etc, thought happy days I can plug it in and find out what's wrong...


Egr valve had failed, got that replaced for about £400 which fixed the limp mode issue, BUT starting when hot and knocking was still present - pretty irritating. Lived with it until its service.


Garage suggested could be the battery, starter motor, or DMF and started with battery.


Appears the battery fixed it! Didnt have enough power to run the starter properly, so even though it wasn't dead, it just didnt have the oomf needed to get the engine started on occasion.


It's also fixed my stop start (hasn't worked since I bought the car!!)


Got the cambelt and water pump done too (103k and not done lol!)


Expensive, but she's back up and running!!