custom90 wrote:

Any possibility of any obstruction sucked in the air intake, inc to the air filter?

A workshop glove, leaves, blue paper roll, or similar things can easily r go in.

Long shot, but is possible.

I Like Old Skool wrote:

Could be the fuel lift pump, but not for the reason you might think....

My 300tdi was intermittently losing power when on the motorway at full speed of around 85-90mph, so full fuel flow required. This suddenly got worse after an off-road foray.

I found out that the fuel lift pump was not working, but that wasn't the issue either. In the fuel lift pump is a nylon gauze strainer and this was clogged up with crap from the tank. While waiting for a replacement pump to arrive I cleaned the muck out and refitted the non-operational lift pump and full power was restored.

Turns out (and I read this on the internet too, so it must be true) that the type of injection pump used on our Tdi engines will suck its own fuel quite happily without the lift pump. My experience suggests this is the case.

When the fault first showed up the flow must have only been restricted enough to be noticeable when driving flat out for a while where the fuel filter got drained and fuel being pulled through the partially blocked pump strainer was not enough to refill it. Once more muck was dislodged and blocked the pump even more the problem got worse and the engine would splutter, shake and cut out, but would then restart after a couple of minutes and if allowed to idle for a bit (allowing fuel to seep through while using minimal fuel for the engine) I could then drive another mile or so before it would start struggling again.

It ran fine with the failed pump fitted while I got around to fitting the replacement.

This fuel strainer in the lift pump isn't mentioned in any of the service manuals/schedules I have ever seen so it was a surprise to me but always worth checking it occasionally as it is only 1 screw to remove the cap from the lift pump. Because it is upstream of the fuel filter it will catch any lumpy bits that might be picked up from the fuel tank and only lets finer stuff through to the fuel filter.

anotherrick wrote:

First of all thanks to the replies above. I took a look and all pipes appear "ok" for thier age.
However the issue has occurred five times over the last several days and it's definitely fuel related. I know this from the very strong smell of fuel i can now smell when it happens. Same symptoms as my first post but it only seems to happen when the car has been driven at higher speeds i.e. duel carriageway/motorway speeds and only happens when coming off the throttle to slow down. Then will just about idle or ill turn it off for a couple of mins then it'll start fine and I can carry on.
So far anything below 50mph and I can drive round all day long.

Well, 50 mph is quite a bit more than walking speed

Could be thé turbo then. There's a guy experiencing the same issue on his Puma. He's doing a lot of investigation / testing in order to sort this out. Just look in the tdci section.