2003 T4 2.5tdi not always making boost.

[TMWNN]

Hi all.

As per the title I'm noticing my van is only making boost intermittently, more often than not it doesn't.

The engine is purring like a kitten otherwise, it doesn't really affect how it drives other than the lack of power, no running rough etc.

I'm a bit lost as to what might be the problem. Pretty sure there isn't a boost leak as I can't hear anything and it does make boost sometimes. I've also replaced all the vacuum piping attached to the turbo and wastegate etc as it was a bit brittle from heat cycling but it has made no difference.

I suspect perhaps the wastegate is somehow stuck open and sometimes for whatever reason it shuts properly hence the intermittent boost. Anyone heard of this problem with these cars, known issue?

As an aside the tube at the base of the airbox that it pulls in air through has a pretty small ID and seems like it would be pretty restrictive, anyone experimented with removing it?

Thanks in advance.

[Umai Naa!!]

Tube at the bottom of the airbox is a water drain with a one-way flap on it.

Replace all the vacuum lines on the motor, and see how you go. You'll probably need a few metres of hose, and in a couple of different sizes. The original stuff rots out.

[TMWNN]

Thanks for correcting my assumption on the airbox tube, feel like a bit of a dill now

I've already changed all the vacuum hoses to fresh new ones and it doesn't seem to have helped unfortunately.

[Seano]

Partially blocked intercooler?

[TMWNN]

I noticed today that it seem to make good boost when the engine is cold but then stops as it warms up. I'm still thinking the wastegate is the likely culprit. Maybe as it heats up it doesn't seat properly and is partially open allowing the exhaust to escape?

I guess I'm going to need to take the intercooler off and have a closer look.

[TMWNN]

So after a bit more research on this I'm now thinking the MAF might be the problem, the lack of codes being the giveaway factor. I know on my Subaru the MAF is an $800 part from Subaru Australia but can be orederd from japan or america for more like $200ish.

Whats the cheapest way to get a genuine VW part?

[Sunny43.5]

Whats the cheapest way to get a genuine VW part?[/QUOTE]
I suppose some sarcasm is warranted here you could try and mortgage your house or donate a kidney to someone , but in all honestly you might find a better price in the UK I would join the Brick works VW forum and do some asking , it's free to join after all . Good luck with your quest .