Over boosting

[JLA]

We have a 110bhp tdi and it suffers from the over boost problem, I had it checked by a garage and they said it could be a number of things, of which all have been covered on here too.

My theory is, if there was a fault with the turbo would it not cut out every time it reaches a certain pressure or drive at a certain amount of revs etc? Instead it seems to do it randomly, sometimes it won't do it for a day or two and other times it does it every time you put your foot down.

Also I noticed it feels like its hessitating/a little flat sometimes, even at low speed which makes me wonder whether it could actually be a sensor or something that controls the turbo?

I've changed the vac pipe from the actuator and that hasn't helped. Could anyone tell me what else to check/try before I start looking for a new turbo.

Thanks.

 

[h100vw]

Is the actuator stuck/sticking closed? A scan with VAG-COM would most likely throw up a culprit

Gavin

 

[domburg]

had this too on my olf golf gt tdi, in turns out the actuator was seized, however it may be just the MAF, run VAG COM on it as stated above

 

[JLA]

I had a look at it last night and tried to move the actuator by hand, is it meant to be hard to move or fairly resistance free? Also, does the rod push or pull against it. I'm guessing it pulls seeing as it has a vac pipe? With this said, if its meant to be fairly resitance free then I think there is a problem with it because I could hardly move it.

domburg, how did you sort yours out, Audi said they can't get just the actuator, is it repairable? Also, what is a MAF? I don't know anyone with a vagcom or get chance to take it anywhere that could do it for me.

 

[domburg]

from what i gather, (dont quote me), i think it should be able to be moved fairly easily, a brand new turbo was put on it to cure it, however im sure you could get it re-built but it depends on cost i suppose.

the maf is the mass air flow sensor, its part of the pipe from the air box to the throttle body

dom

 

[h100vw]

The actuator on the big turbo conversion I bought was set to 28PSI, a bit on the heavy side of a petrol car. You could move the actuator by hand no problems. I can't remember which way it went though and a diesel turbo may be different.

It would take a while but I think you could remove the turbo or possibly the downpipe and free up the actuator.

Gavin

 

[VRStu]

Sticking VNT vanes is quite common. It does normally occur when you give it a bootfull.

 

[h100vw]

Sticking VNT vanes is quite common. It does normally occur when you give it a bootfull.

Another good call.

 

[JLA]

Thanks for all the info, but I have more on this...

Driving along normally it does it too, not accelerating or going fast, just normal 60-70mph for no reason and also I can feel it 'hunting' a little too, both of these could be due to the sticking vanes. But, when I accelerate I can hear a shhhh noise (for want of a better explanation lol). It sounds like a blow off valve of some sort and keeps on going until I take my foot off the throttle or it goes into limp mode. Its not the noise of the turbo spooling up as I can hear that too.

 

[JLA]

Can anyone recomend an ebay vag com that comes with everything I need so I can check the fault codes myself??

 

[h100vw]

I bought an ebay cable years ago and then got the real thing for the full access and ability to do CAB BUS vehicles.

You should be good with any of them really, just be aware that it often takes some messing about to get them going the first time. USB drivers are the usual snag.

I wonder if there's 2 problems, something sticking causing high boost and it is then escaping from somewhere? Which is what you can hear.

I think that taking it to a VW specialist would be worth the trip.

Gavin

 

[JLA]

I think I'll Just see if I can trade it in today. I've had no end of trouble with it in the 2 years I've had it and now I've had enough.