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VW Sharan 2.0 TDi (140) Turbo cuts in and out



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#1 JimmyUK

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Posted 20 July 2017 - 07:09 PM

Hello,

Hope someone here can shed some light on this weird problem I’m having with a 2006 VW Sharan 2.0 TDi 140 BHP (136K miles) ... I know it's no Golf but does have the TDi Lump at least!

The turbo seems to cut in and out during acceleration. I’ve replaced several parts now and costs are adding up! :S

 

Actuator Valve (N75?)
Main vac hose pipe (7M4611931R) had a slight split in it.
2x Boost pipes (see image below)
EGR Valve

 

I’ve tested the actuator with a hand vac pump and it moves freely and also it holds its vacuum when left connected. I have a VAG COM and have ran the test on the Actuator Valve, the engine changes tone, so one can assume that it’s doing its job.

 

I’ve changed the EGR valve to a new one. This improved the performance slightly however did nothing to cure the turbo surging.

 

I’ve checked the intake to the turbo for excessive oil, none looks clean. The turbine also spins freely.

 

The car is serviced every 6000 miles (twice a year) and has been since I’ve known it from when it was a couple of years old.

 

I’ve checked over all the boost pipes, replaced the one just before the boost pressure sensor and then one before that that links to the intercooler (Parts 17 and 6 on the diagram below). They separated once and looked like the lugs were worn, so just changed both.  

diagram.PNG

 

I’ve captured from the VAG COM graphs that clearly show the requested boost and the actual boost fluctuating under it. You can clearly hear the whoosh of the turbo then the release of the pressure in time with the graph. There are no fault codes on the ECU, never goes into limp mode.

 

grab1.png

 

grab2.png

 

If anyone can suggest something that maybe the issue or can point me in the right direction please do comment. If there’s any further info or data that I may have missed, again let me know.

Kind Regards,

 

Jimmy (UK – North Nottinghamshire)




#2 gazman70

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Posted 21 July 2017 - 09:22 AM

It could be a sticking VNT mechanism giving you erratic boost you said you used a hand vac to test the actuator the problem with that is you cant feel for any grittiness if you can get to the actuator by hand and feel the movement it would give you a better idea as to its state as a former Sharan owner that had VNT problems i know that's easier said than done there's not much in that engine bay.



#3 JimmyUK

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Posted 21 July 2017 - 09:30 AM

I've managed to get the plunger by hand and it does seem to move freely not stiff nor gritty in it's movement.

 

Yep not the easiest car to work on! With the car supported high enough i'm able to get under the car and move the actuator by reaching up behind the engine. With the sound of the engine changing when I run the actuator test on VAGCOM wouldn't that suggest that the VNT is working or is that wishful thinking?







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