I've noticed that even on a very small incline, when facing uphill, the car has a rough start. What might be causing this? (vRS TDI ) 

Sounds like there's air getting into the fuel system causing the fuel to drain back into the tank.

 

I had this issue on my previous Saab (1.9 Fiat/Vauxhall engine) and it turned out to be the leak-off pipes from the injectors. They weren't leaking fuel (as there's no pressure in them) but the rubber had gone porous and would let air in and cause the engine to chug and run lumpy on a cold start.

Is this a possibility? Since it only happens if facing uphill.

Can you see whether it is still doing it if you turn the car around and park it downhill?

No, it is not doing it. That's why I've asked.

Might it be a fuel filter problem? I'm about to change it anyway in the following days since I think it's due. Don't know when it was last serviced.

Edited 3 June, 20215 yr by BogdanB

Do you meana rough start as in the engine not starting correctly? Or rough start as in starting to drive away when going uphill?

Engine cranking a few good times before starting. No driving involved

It sounds like either the fuel pump is failing, or the fuel non-return valve has stopped working.  Please also check the fuel filter.  In the TDI's - they need checking/replacing every 20k miles.

Edited 4 June, 20215 yr by varaderoguy

Thanks for the suggestions. The fuel filter will be changed asap.  May I also ask where the fuel non-return valve is located? 

By checking this I'm guessing it's the 'damper' ? 

Edited 4 June, 20215 yr by BogdanB

There are several valves to content with; there will be a valve in the Fuel Pump in the Fuel tank - and there should be a valve in the fuel line - and finally a one-way fuel flow in the Fuel Filter (which is that great big black cylinder at the front of the engine bay).

There’s an issue with some tdi’s that they take longer to crank. Some have had updated software to rectify. Could be that. Also believe the fuel filter is recommended for change at 40k miles.