B8 3.0 TDI Turbocharger Underboost Problem.

[Tommy Pickles]

Hi guys, first post on this forum and not sure if I'll get the help I need. I have a 2008 A4 B8 3.0 TDI. The problem I'm having is inconsistent boost. Sometimes it pulls ok (mostly above 2.5-3k) other times I'll get an Underboost code. I've had a garage look at it and try an fix the problem. He has tried:

Replacing the swirl flaps (one side had failed)
Done a smoke test - apparently found no leaks
Sent turbo off for recondition - apon inspection they found nothing wrong with it apart from a slightly worn actuator arm.
Replaced MAF sensor.

Nothing seems unusual in his diagnostic tool (not vag com)

Like I say sometimes it can perform ok (wouldn't say full boost) and other times it won't boost at all. There doesn't seem to be any clear indication as to why it is so inconsistent.

Does anyone have any other suggestions? Or have any experiences with this?

Not to familiar with diesels but willing to try and diagnose anything people throw at me

Thanks in advance.

 

[desertstorm]

If you use VAG-COM then there is a lot of information associated with the fault that may give you a clue as to the issues. You would have been better off at a VAG specialist. Have you thought about changing the actual MAP sensor itself? .
Where abouts in the country are you ?

 

[Tommy Pickles]

I'm on the Isle of Wight mate. What would I be looking for in vag-com? Specified Vs actual boost? Map sensor was the next thing I was going to try.

 

[Tommy Pickles]

Another note, never really get boost in 1st gear.

 

[Tommy Pickles]

Bump