Turbo problem 1.9 tdi

[Angie]

Hi,
I have a A6 1.9 tdi 110bhp with a chip making it 138 bhp. It has done 149,000 miles with Fsh and has worked fine until recently.
The Problem is as follows:
Sometimes from start up the turbo does not work and will not work until you turn it off, leave it a couple of seconds and start it again. This may take several attempts. Once the car starts and the turbo is working it keeps on working for duration of the journey.
Conversely, if the turbo isn't working, it will not start working during a journey until it has been switched off as above.

I have had a MAF problem before, but this seems to be a different problem.
(But does seem to be Electrical.)

I have tried the Search button but nothing came up that was looked too similar.
:1zhelp:
Please Help

[Dave Avant]

What makes you think the turbo isn't working?

You won't know if it is or isn't until you drive it and performance is severly lacking. A turbo is mechanical and either works or doesn't. Unless it is a problem which is creating lack of performance and thus makes it seem like the turbo isn't working.

What symptoms do you have?

[adamss24]

Have your car scaned for faults codes as there is a problem that triggers Limp mode and the ECU its "turning off "the turbocharger aka reduces fuelling to prevent damage to the engine . Turning the ignition on and off clears the ecu memory, until it happens again. I would check the VNT(turbo) mechanism to see if the rod moves smoothly as if its jammed it will trigger an overboost condition similar to your problem. To remedy a jammed vnt actuator you will need to take the turbocharger off and clean the inside until the actuator's rod moves smooth .Clean the intake manifold as well as you there.

[Angie]

Have your car scaned for faults codes as there is a problem that triggers Limp mode and the ECU its "turning off "the turbocharger aka reduces fuelling to prevent damage to the engine . Turning the ignition on and off clears the ecu memory, until it happens again. I would check the VNT(turbo) mechanism to see if the rod moves smoothly as if its jammed it will trigger an overboost condition similar to your problem. To remedy a jammed vnt actuator you will need to take the turbocharger off and clean the inside until the actuator's rod moves smooth .Clean the intake manifold as well as you there.

Thanks,
This does seem to have these symptoms. I can hear the Turbo when it's working and when it doesn't it pulls very poorly needing to give it large amounts of throttle with very little response. I'll take a look at the actuator this weekend. Would the VSV that controls the actuator (I think) be a possible fault? I have bought a new Air Mass Meter too just in case, but I'm thinking that will now be a useful spare!

Thanks again,

Angie.

[Angie]

I found this site that was very helpful. You may have to register to use the link. There's loads of in depth tech data on there.

http://tdiclub.com/TDIFAQ/TDiFAQ-8.html#e

[adamss24]

Hi, the turbocharger solenoid valve could give the similar simptoms but it will also set codes in the memory. If you have a friend with a vag-com (scanner) then select engine then select adaptation and go to measuring block 10 and see if the VNT rod moves smoothly when cycled on and off by the computer. If it jams then the turbo may have to cam off for cleaning the internals. Have a mechanic do that as its a fiddly job not difficult but fiddly.

[Angie]

Thanks for being so helpful everyone.

I'll let you know how it pans out.

[MartinPCWard]

Dont know if this is any help or relevant but when I got turbo problems I aso wondered about the VNT. I got my wife to sit in the car and hold the revs at around 2k: I then pulled the vacuum pipe off the VNT. As I connected it back again I could feel the rod moving quite smoothly - so in my case I discounted this as a fault. Maybe crude but this tells you if the mechanics seem to be working. If you listen carefully you can here the change in pitch from the turbo as the vanes move.

[kotty]

Dont know if this is any help or relevant but when I got turbo problems I aso wondered about the VNT. I got my wife to sit in the car and hold the revs at around 2k: I then pulled the vacuum pipe off the VNT. As I connected it back again I could feel the rod moving quite smoothly - so in my case I discounted this as a fault. Maybe crude but this tells you if the mechanics seem to be working. If you listen carefully you can here the change in pitch from the turbo as the vanes move.

I see, my mom hear the change in pitch from the turbo, same problem..She can hear the turbo when it's working and when it doesn't it pulls very poorly needing to give it large amounts of throttle with very little response.Anyway, I have bought a new audi 5000 radiator (http://catalog.overnightradiator.com/audi-5000-radiator.html) too just in case...

[Angie]

Right - update!

Still have this problem. I'll recap the symptoms:

Turbo sometimes works - sometimes doesn't.

If it works on startup it will work until the end of the journey.
If it doesn't work on startup, it won't suddenly start working during the journey - HOWEVER - if I turn the ignition off and then back on again at the key whilst rolling, (and usually if the engine has warmed up fully) it has a tendency to start working - this leads me to believe it could be an electrical component at fault.

I have had someone start the car up whilst I have been touching the actuator rod. When it is one of those occasions when the turbo decides to work, the rod moves smoothly. When one of the occasions where the turbo doesn't work, it doesn't move at all.

So I believe the rod to be ok, but whatever provides the pressure to the actuator diaphragm is not providing the said pressure - someitmes.

I've replaced the solenoid valve that provides the pressure to the pressure reservoir, but the symptoms are the same.

Any more ideas?

I had it on a vag-com a while back but i'm not confident that the guy operating it was all that sure about what he was doing. HE said he thought it was 'something around the solenoid valve' that I had already mentioned to him.

Getting desparate now!

[ini]

Have you checked the VNT boost control valve?

It is at the other end of the tube connected to the vnt vacuum capsule.

[Angie]

Is this the valve that is electrically operated and has 3 hoses attached to it? (one hose narrower that the other 2) I believe it's a solenoid valve so that when it energises, it allows the pressure to equalise across input/outlet? (I'm thinking the 3rd hose may be some kind of a pressure reference feed to somewhere else in the system)

Maybe I'll take a pic!

[ini]

The valve oscilates at different frequencies, allowing the electronic control signal to be converted to a variable vacuum control signal.

If it is blocked, damaged or incorrectly plumbed in, limp mode will result.

http://i118.photobucket.com/albums/o99/inisj/N75.jpg

[The Mad Locker]

Sounds like your N75 valve to me.