Likely to be something to do with the flooded plenum chamber which can cause havoc. Are you sure you have sorted the drainage? The seal rots between the plenum chamber and the car interior and the brake servo can rust through due to the immersion in water - can even draw water through the vacuum pump.

Electrical contacts and components corrode all over the place so everything needs checking - I'd also remove the carpets to check everything electrical under there and properly dry out!

I doubt if it is the fuel filter. When the car was working not working what was the weather doing? - just a thought

Edited by Big John on 12/04/2019 at 22:31

Make sure you check under the front passenger carpet.

There is thick foam under the carpet which holds loads of water, then underneath all that is the CCU ECU which will be laying in water.

The plugs go green then wires start to fall off.

Pull it out then check inside the CCU for water.

The P0230 fault is fuel pump primary circuit fault.

This will give you the cutting out problem, fuel starvation.

The pump is under the back seat on top of the fuel tank, but cables run down under the carpet so may have been affected by the water.

Edited by dieselnut on 13/04/2019 at 15:42

Thank you for your reply, I'm taking the whole carpet up on Monday and checking/dryingeverything so I will report back and let you know.

Check the original source of the water as well - remove top of the plenum chamber and the battery to really make sure the drains will remain clear.

Also thoroughly check the brake servo for signs of rot and read this as I think with this age of Audi A4/A6 the setup is nearly the same as the Superb mk I :-

https://www.briskoda.net/forums/topic/152490-water-ingress-problemsolved/

Electrical problems after water ingress are well documented. When removing carpets be careful with any connecting wires and PHOTOGRAPH/document everything especially electrical connections. The reason is - it is possible for corroded wires to part company and it's quite hard to work out which colour wire connects where! As above check for water in the CCU.

Good luck

Edited by Big John on 14/04/2019 at 23:26

Er - I did - was just trying to show it was between plenum and interior as this is the water that leaks in.

Edited by Big John on 15/04/2019 at 13:59

So, I took up the carpets and there was literally a couple of litres of water submerging the wiring under the carpets. I couldn't see any particular damage to the wiring but I got all the water out. I checked the CCM and this was bone dry inside luckily. The car is now starting and running without any particular issue but due to the previous stalls, I've lost my confidence with driving it until it's been given the all clear so I'm taking it to my local garage tomorrow for a proper check. Thanks everyone for your help, it us much appreciated.