Possible flood damage - what to do ?

[b206]

So I was on a long journey yesterday - had to pass through quite a lot of water. The last section of flooding was going smoothing until a <removed> truck driver ploughed through the flooding at pace. The bow wave was well above the bonnet (about 30cm up the windscreen). I felt the car pop up for a second - I kept an eye on the revs which started to flicker (thought that was game over!).
I have driven it about 30-40 miles since - but the revs flicker around 1100, no longer smooth. I have no idea what to do - should I book it in with Audi ?

I removed the air filter which seemed dry - but there was a bit of water in the air box and intake (no water from the filter up).

Its an Audi A4 3.2l V6 Avant.

Suggestions much appreciated!

[theskyfox]

To be honest I'm surprised you went through water so deep, its such a risky exercise and such a potentially expensive mistake. Modern cars like these are covered in sensors which are all electrically powered and do not play well with water.

Your best bet is to go to a garage/dealer and get a fault scan done. The ECU controls the revs based upon the sensory inputs (e.g. The Mass Air Flow sensor). If any of these break or become faulty it can cause problems like you describe. Hopefully it'l just be a sensor that needs replacing. If you had got water into the engine, itd probably have been a total writeoff regardless of age.

-Andrew

[zollaf]

a tiny bit of water entering a cylinder will cause a con rod to bend. sometimes it will come straight out through the block, sometims it will run lumpy for a bit until it blows. its lumpy because one cylinder is down on compression. if it goes, a new engine will be required as the block will have a big hole in it. of coyrse it could be a sensor, but how do we know and do you want a 5k bill. i would stop driving now and get it sorted. a compression check will tell if a rod is bent.

[Phil K]

I think a full check is the best thing you can do like others have said... driving it now will only worsen the problem / extent of repair.

Personally, I'd look around for a local recommended audi specialist rather than go marching into Audi - could save you a chuck of cash in the long run!

[b206]

Thanks for the replies - I'm unfortunately away so need the car, looks like I'll be catching the train instead. I have tried both independent garages and Audi - all of which don't have any free slots until late next week!
The flood wasn't that deep, but the oncoming truck was driving one hell of a wave - sods law I suppose!

[markp306]

...driver ploughed through the flooding at pace. The bow wave was well above the bonnet (about 30cm up the windscreen).

Shame you had no opportunity to get his number or some other evidence, but obviously your immediate concern was the car. That has to be a case of driving without due care and attention then?

I have an app on my screen mounted phone that records video and location, etc, and I'll certainly make sure its on more often, based on your recent experience! As it happens, the last recorded clip has some tw*t in a Range Rover mounting the pavement, coffee in one hand, barging through a single-file narrowed road!

[b206]

Well went into a VW/Audi specialist yesterday - they couldn't find any faults in the diagnostics. Gave it the once over and said all is ok.
I've since driven 300 miles without any issues - I just need to find out why it doesn't hold steady rpm. Also changes at higher rpm - was in 2nd @ 3500rpm before it changed up to 3rd - usually in 6th before then!

[zollaf]

did they carry out a compression test ? did they give you a letter saying it is fine to drive and if it does go bang due to a bent rod then they will pay for it ?
i am not saying it does have a bent rod, but i have seen this happen before and it is avoidable having to replace a block, if the fault is found early enough.

[b206]

No compression test - they said a bent valve/rod would result in a misfire error in diagnostics ?
Anyway, car is due a service shortly so I'll ask Audi to check it out.