Hi,

 

I did my brake job over the weekend and also ran a can of liqui moly diesel purge through the engine. After a few gentle miles getting the new pads n discs bedded in and the engine warmed up I opened the throttle a bit on a fast ‘A’ road. 
 

I got a severe judder in 3rd gear at around 3k and an intermittent issue where the car would not rev past 3k. 

 

Performance in 2nd is also a bit suspect when the revs get up. 
 

in the higher gears 5th and 6th the car cruises along happily at 100kph...
 

The car runs sweetly in neutral and will rev to the red line. With no hesitation or splutter. I’ve checked for fault codes and there are none.
 

I suspect the not revving past 3k is the ECU putting the car in to limp mode. 
 

If just tootling around town the car is fine. The issue begins with higher revs and possibly a demand for boost. 

Thoughts... I have had a trawl through some old posts and the Clutch and DMF pop up as possible causes along with intercooler pipes. If the issues was the DMF / clutch I wouldn’t be getting the limp mode issue as the revs would increase with little increase in road speed.

 

Thanks for listening...

 

John
 

 

Ok quick update.

 

I checked the boost pipes as I taken the 90 degree elbow off to Acess The brake master cylinder reservoir. The elbow has gone back together ok and I cleaned all of the oil n crud of of it. 
 

A check of the plastic pipes down to the Intercooler shows these are also solidly attached. 
 

Could my issue be a gummed up Turbo??

Yes, sticking vanes are a distinct possibility.

 Get a Bluetooth OBD2 dongle, plug it in the socket, install Torque on a phone and look what your boost is doing while driving.

2 hours ago, KeithCheetham said:

 Get a Bluetooth OBD2 dongle, plug it in the socket, install Torque on a phone and look what your boost is doing while driving.

 

Before that he can use one (bluetooth ELM327) to pull fault codes.

I have pulled fault codes with a simple Bluetooth / wifi scanner. 
 

There are no fault codes....

There won't be with sticking vanes, you need to log boost while driving.

Ok I did think you might get an over boost fault code. But easy enough to log the boost.

No overboost because the vanes sticking leads to underboost, and less boost won't throw codes.

21 hours ago, Johnsnz said:

liqui moly diesel purge

What issue prompted use of this product? Just read the literature with product. It is designed to kill off.microbe growth in any water at bottom of fuel tank.

 

If the turbo vanes are stickING what can be done to rescue turbo before they seize?

26 minutes ago, bmbmdmb said:

What issue prompted use of this product

I’ve given the car a full service oil and all filters.  Plus the brake refresh. The liqui moly was aimed at ensuring the injectors were cleaned. 
 

The engine was starting and running sweet prior to the liqui moly and continues to start and run sweetly following the treatment.

 

This juddering and boost issue is new...Although manifesting itself after the treatment....
 

 

https://www.audi-sport.net/xf/threads/un-sticking-your-tdi-vnt-turbo-vanes.107121/

Could some 'sludge' from bottom of fuel tank have broken loose and restricted your fuel filter? Rather than a turbo vane problem? Revving engine in neutral is not going to use same amount of fuel as under load in gear at 3k rev where you are having problems?

I'm interested in reason you think your injectors were dirty? Or preventative maintenance? I was reading about fuel additives on some other forums etc and opinion is divided but to clean injectors of hard carbon I think they needed removing. On a petrol astra 5 with vvti sensor issue the use of BG44 worked well to clean sooted up injectors, but this was not yet hardened carbon.

https://www.audi-sport.net/xf/threads/un-sticking-your-tdi-vnt-turbo-vanes.107121/

Thanks Sep - 

Edited 28 October, 20196 yr by bmbmdmb

It’s was preventative... I fed the liqui moly direct from the can into the engine not via the fuel filter. Which is new with less than 500k of running time...

Fuel injection pressure on a PD is so high that injector clogging isn't normally possible, however bypassing the fuel filter is extremely unwise since there may be particles in the snake oil which would otherwise be trapped in the filter which have now actually clogged the injectors.

I think you may have made a serious mistake, injector cleaning on PD and CR engines is simply not necessary because the fuel itself already contains cleaning additives and injection pressures of thousands of bar flush the pintle clean with every injection cycle.

32 minutes ago, sepulchrave said:

 

I think you may have made a serious mistake, 

Maybe, Maybe not....

 

If you hunt around the web enough you get a variety of opinions. That’s part of the fun of online car issue diagnosis...

 

Its somewhat similar to the varying opinions on the use of Mr Muscle on VNT issues. Some say it’s a great solution some say it’s not and a strip down and turbo rebuild is the way to go.

 

 

 

 

15 minutes ago, Johnsnz said:

Maybe, Maybe not....

 

If you hunt around the web enough you get a variety of opinions. That’s part of the fun of online car issue diagnosis...

 

Its somewhat similar to the varying opinions on the use of Mr Muscle on VNT issues. Some say it’s a great solution some say it’s not and a strip down and turbo rebuild is the way to go.

 

 

 

 

 

I've been on here long enough to know that the oven cleaner trick often doesn't work, but I'm equally certain that a turbo rebuild done properly always works.

 

Snake oil never fixes anything, at best it does no harm.

 

Let's hope you can fix your car which didn't need fixing before you fixed it with snake oil.

18 minutes ago, sepulchrave said:

 

Let's hope you can fix your car which didn't need fixing before you fixed it with snake oil.

Super helpful. Thanks for that.

Try manually working the VNT mechanism to see how free/not it is, and to maybe dislodge some carbon build-up.

8 hours ago, Johnsnz said:

Super helpful. Thanks for that.

 

Adults take responsibility for their actions and I have been trying to help.