?water in fuel

Hi when engine is idling, it has started to miss and revolutions fall away in the 14 years I have owned the van it has never done this, filled up with fuel before going off
So wondering if fuel is contaminated and if so what can I do to rectify
Thanks
Mike 
VWt4

What engine do you have - diesel or petrol?

Hello thanks for reply, the engine is 2.5litre five cylinder petrol
Mike

Ian H
Have not checked for fuel filter as yet, yes the engine runs wel under load, it is petro
Mike

Many years ago I got water in our petrol campervan. We we're having a holiday in Lincolnshire and there had been some heavy rain in the morning.  I stopped at a rural petrol station for a petrol fill up. I'd only driven a couple of miles down the road before the engine stated to cough and splutter. Carburettor top off revealed water in the float chamber, after cleaning up with kitchen roll we were back on our way.

I ended up owning a cheap 2nd hand Skoda in the 1970s, a "gift" from a relative after petrol rationing was called off when the OPEC crisis was resolved, he'd no need for the extra petrol coupons that came with the banger. The Skoda's petrol cap didn't make a good watertight seal, so not infrequently following heavy rain I'd have to clean out the float chamber, to remove the water before it would properly start and I could drive home after work. Happy days then , I'd probably be more irritated now. The strange system on the Skoda to adjust the fan belt tension using washers comes to mind whenever I see the James Bond film when Sean Connery is in Moscow and they have to hit their car engine with a hammer to get it started.

In your position I would do a search on the UK T4 forum and then ask questions there if there are no obvious existing threads that cover the issue. Water in the fuel is not the first thing I would consider, because typically on a fuel-injected engine it will just stop the engine - but that's more applicable to diesels, which all have a water trap feature to prevent it happening. I suspect that petrol engines may a bit more tolerant of small amounts of water in the fuel, but it's still not what I would look at first.

I can recall a similar issue on the last 5-cylinder petrol engine I owned (in a Passat) and that turned out to be a problem with the MAF sensor, but that's just one of several things that could be the cause.

A though on this matter. If there is water in the fuel it will show in the fuel filter. It’s not very common these days but can happen. 
A friend of mine had a similar problem with a VW Sheran people carrier. Sudden loss of power and misfire. It was traced to a faulty coil.

Thank you all for your replies will look into all of them, looking back over the journey home when all this started I was coming uphill by the "hole of horcum" which is a 1 in 10 gradient, I ended up behind a cement lorry and had to do nifty gearchanges and a lot of revs, after that, the problem started so now wondering if I dragged up dirt into fuel filter, and that looks like the original one, so checked fuel, no water present, filter next
mike
vwt4

Management has just reminded me that she had a similar  problem with her Mk1 Escort. Cutting out on hills that started when she was on holiday in  the Robinhoods Bay Area. That was rust in the tank. 
We watched the bus  climbing up to the Hole of Horcum yesterday. By the time it got to the top there was a good convoy behind it. At least you made it to the top.

Only just Dave only just
Mike
Vwt4

ok friends
I really need help with this, garage had van for several hours yesterday, fuel filter replaced, fuel checked for water none found throttle housing checked a little wear but not serious various vales checked and cleaned, returned to to me in the same condition, they told me I need a VW trained mechanic, what is any ones thoughts on this please
mike
vwt4
ps been to vw forum no one bothered to answer

vwt4 wrote:
ps been to vw forum no one bothered to answer

You have to be persistent and patient there, but there are plenty of people on that forum that know a lot about the subject (I'm not one of them - I know a bit about T5s and stick to that part of the forum). As with any forum, the vaguer the question, the vaguer the answers, so any solid diagnostic data you can give them will probably improve the chances of a response.

I'm not sure how much diagnostic data you can access on a van of that age, but on more recent ones you can use a diagnostic tool called VCDS which will let you look at all of the sensors in real time. However, you have a complex, fuel-injected 5 cylinder engine, so there are lots of things that could go wrong - air flow, pressure and temperature sensors, cam position sensors, fuel temp, fuel pressure, TPS, EGR, etc etc. - so guessing really won't help.

If you don't have the tools and/or the inclination to do further diagnosis yourself, I don't think you have any other option but to find a garage locally with experience of VAG engines of that age, and trust in them to find the cause.