Tdi turbo cutting out.

[crankedup]

Our Skoda 1.9tdi is presenting a problem that is now becoming more frequent occurrence. The turbo keeps cutting out when we go on a longish dual carriageway/motorway trip. We understand this to be a fairly common problem on this engine, pulling in and switch off and back on seems to re-boot it and all is well for a time.
The car is very old (2003) with 172,000 on the clock, getting to the stage maybe that its getting time to buy another daily hack. Is the turbo problem likely to be an expensive fix? Otherwise the old car seems to be just fine.

[annodomini2]

Get the free version of this:

http://www.ross-tech.com/vag-com/

And one of these:

http://www.ebay.co.uk/itm/New-Car-Diagnostics-USB-...

Do a fault code readout, with such a vague description it's impossible to tell.

[wildoliver]

Probably n75 valve to be honest.

[crankedup]

wildoliver said:

Probably n75 valve to be honest.

Thanks guys. Erm, what is a n75 valve (sounds expensive)?

[coetzeeh]

My Golf 115hp tdi showed similar symptoms. Whenever I travelled at 80mph+ (in Germany) and came off the throttle the car behaved as if there was no turbo when attampting to speed up. Stop, switch off and start - presto.

I started using premium diesel only (as opposed to supermarket cheapest) and diesel additive and after 3 tanks or so the problem has gone away.

[TheSnodgrass]

Either a DPF (Do you have any warning lights?) Or an N75 valve as said, Valve isnt really that expensive, DPF on other hand tho is rather heafty.

[TheEnd]

I imagine it would be a vane controlled turbo, and inside there will be a number of blades around the edge that direct exhaust gasses in towards the turbo compressor wheel.
When it wants power, the exhaust is directed over the wheel, when it wants to reduce boost pressure, it'll move the vanes so the majority of the gasses go around the outside.

This moving of the vanes is controlled by a vacuum powered actuator, and the N75 is the name for the valve that allows a certain amount of vacuum through to move the blades into the right position.

There could be a few things causing it, but it could be that this vacuum valve is faulty, leaving the vanes stuck creating more boost than is needed, and when the ECU realises this, it goes into a limp mode by injecting less fuel and limiting power.

The fault code logged would be the best to figure out what is happening.

[Sardonicus]

Could be sticking variable vanes on the Turbo causing an overboost condition (a common VAG problem ) this will cause the car into limp most an ignition on/off will often get round the fault for a short period till the ECU realizes the fault is still present

[crankedup]

Thank you to all posters for advise offered particularly 'Theend' for a more detailed post. Seems the engine displays this problem on a very variable basis, one trip and turbo cuts out three times. Identical journey another occasion and it behaves without fault. As advised I will have it 'plugged in' for full diagnostic. Thanks again.

[marked1]

Sticking Vanes most probably.

Mr Muscle will be your friend. Spray some into the turbo itself and wiggle the actuator up and down. Sounds like a piss take but isn't.

Did it 10k miles ago on my TDI with the same symptoms and mine still works perfect now on 165k miles

http://www.audi-sport.net/xf/threads/1-9tdi-sticki...

Edited by marked1 on Saturday 15th November 18:46

https://www.youtube.com/watch?v=PbUAfzi5BdM

Edited by marked1 on Saturday 15th November 18:48