A4 B6 1.9 TDi 130 losing power after driving downhill

[haaran]

Hi all, help needed!

My B6 A4 1.9 TDi 130 has an odd problem. Recently it has started losing power and going into limp mode almost every journey. It did this previously and I would just restart the car and it would be fine for quite a while. However, now it's potentially a lot more dangerous as this happens mid-overtake on the motorway and I have no option to switch the car off and restart it. Now the odd thing is it seems to happen more when I've traveled downhill and am then attempting to go uphill (the worst time!).

The fault code it's coming back with is 17965 which, according to RossTech, means 'Charge Pressure Control: Positive Deviation'.
The solutions it suggests are:
- Check hoses, pipes aren't disconnected, blocked or leaking
- Check N75 valve for boost pressure control
- Check, Clean, Replace Charge Pressure Control
- Check, Clean mechanism for variable nozzles

Now I've tightened the few hose clips I could easily get to and there's some improvement but I was hoping someone may be able to narrow down the cause perhaps and tell me how I can perform the various other checks suggested.

Thanks for your help

[spink]

Replace ALL the vacuum hoses whether they look ok or not, that will normally sort it . It's also cheap to do.This is probably the most common fault you come across on vag tdis

[haaran]

Thanks.
Are they all the ones on the driver's side of the engine (about 6 or 7 of them) or are there others too anywhere?

[Monkeymagic]

Get VCDS and go into output tests and cause the n75 to start running with the engine turned off. Make sure the actuator rod is moving up and down freely. I would suggest this is stuck vanes in the turbo.
Sometimes soaking the actuator in oil and freeing up using the above method will get it moving again. You then get a huge cloud of soot out the back as you floor it.
This is an overboost code so in other words it is not a leak...

[prj]

In 99% cases on these cars this is caused by stuck vanes on the turbo.
Clean the vanes and everything will be OK.

[haaran]

Would the turbo vanes stick intermittently?
Once the car has been restarted it can drive perfectly for a long time with the turbo boosting fine (or so I think).

[Monkeymagic]

Yes its when you bury your foot under load usually.
Try doing as i say to clear the vanes failing that its as prj says it will require a rebuild and clean.

[ronaldvossen]

Has the problem been solved? Its a common problem with those tdi's... Air mass sensor related I believe.. Or a valve that should shut but remains open until you reset the system by key.


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[Monkeymagic]

Overboost on these is nearly always sticking vanes.

[geryS2]

yep, got that on mine too, did replace all the hoses

minor problem

[macspring]

How do you clean the vanes ?

Thanks.

[haaran]

Mine magically cured itself after a 200 mile drive to Scotland. Sticking vanes were the problem and a long motorway blast managed to free them I believe. I've been using more of the rev range more often and have not had the symptoms since.