Volkswagen: VW Passat SE TDi Engine No.AFN849200, mass air flow, phil pickering

Question
My VW Passat registered 2.9.99 107,000 miles to date.  Fully serviced. recent oil & filter change including air & fuel filter (K&N replacement air filter). Car starts immediately hot or cold & can cruise at 80-100 mph but, when slowed down in traffic the acceleration is so poor we are often left behind.  It also feels as if there is not enough fuel available as it feels as though it is being held back.  I am sure it should run more freely than it does.  It does not use any oil, & there is no smoke evident.  Our local garage has checked it but has not found anything wrong.  We have also treated it to Redex deisel treatment which, for a while seemed to improve things, but at the moment acceleration is dreadful, please can you advise.It gets 47 to the gallon.


Equally annoying, and also checked, is a wheel bearing type hum and drone from the front wheels.  I replaced the discs and pads recently with Brembo discs and Ferodo pads.  The noise can also be described like a motor on an underground train it is constant, when warmed up and the car has been used for a while but is not evident at higher speeds. The road surface makes no difference.

It had the VW recall for the lower suspension arm check and all was ok.

Not having driven a similar car I cannot draw comparisons, but feel that although my local garage were unable to find any problems, all is not right.

When we bought the car the dealer mentioned the vacumn unit which has some control over the turbo and warned that if this fails the car loses a lot of its power, the one on my car looks like the original is there any way of checking that it is working?

I look forward to your reply.
Thank you.
Phil Pickering

Answer
i cannot really advise on the noise, it could be bearing's, tyres, or on rare occasions the differential (found one faulty differential bearing in last 3 years). as for the lack of power, the air mass meter is the usuall suspect, otherwise known as air volume meter or mass air flow meter. these are very common on diesel cars and the effect of replacing is instant (car may blow black clouds of soot out afterwards as trhe turbo is working properly and actually boosts) let me know how you get on. john dempsey.