Sharan Bj2002: High Turbo Pressure - VTG OK?

Hello everyone,

Yes, I have tried searching, and yes, I have tried the suggestions. However, none of them were helpful.

The Sharan has 200,000 km on the odometer. When accelerating with full throttle, the car enters limp mode. The error memory indicates: "Boost pressure regulation limit exceeded."
VCDS indicates that the boost pressure is consistently 0.2-0.3 bar above the target value when the accelerator pedal is at 50% position. Furthermore, above 75% accelerator pedal position, the measuring range of the boost pressure sensor is insufficient to accurately measure the overpressure (2590 mbar, target approximately 2100 mbar).

The trusted VW workshop has already replaced the turbocharger pressure sensor.

I then inspected the vehicle and replaced a leaking turbocharger boost hose. I also replaced the EGR valve, which was extremely clogged and leaking (similar to what was described in a technical article). Additionally, I replaced the vacuum hose to the turbocharger control unit because the hose was worn and thin-walled.
Außerdem habe ich noch die Unterdruckdose am Turbolader entfernt und das VTG-Gestänge 200-mal hin und her bewegt. GIt's totally easy...

Unfortunately, none of that helped. The problem is the same as before.
The fact is:
VTG rod iO.
AGR iO
Boost pressure path blocked (although it doesn't matter because the boost pressure is already exceeded).
Boost pressure sensor iO.
LLM and AGR measurement values are plausible.

Could it be related to the N75 valve? Could it be switching due to excessive vacuum?
Could it be due to carbon buildup? Because I haven't cleaned the intake manifold. There's a gap of about 1 cm in diameter. Could that be the reason why the boost pressure is so high?

I would be very grateful for any tips!

Greetings,
Armin.

You could insert a vacuum pressure gauge and observe how the vacuum pressure changes with the duty cycle.

The evidence suggests a more likely cause is a short circuit (hot short) in the VTG.

Short circuit??
What can be done about it? Should I remove the turbo and grind/clean it?

Greetings.

Quote:

What can be done about it? Should I remove the turbo and grind/clean it?

Okay, for example. However, you should first determine which component is the root cause. Therefore, I would start by checking the vacuum pressure and see if there is a difference in pulse width, vacuum pressure, and boost pressure when the engine is cold versus when it is running at operating temperature.

You might also notice it if you drive it when it's warm or hot, and then perform a pressure test.
When dealing with "hot connections," the "release" under vacuum should ideally be difficult and create a noticeable clamping effect.

Driving on the highway in a car with an ASV (adaptive speed limiter) and a somewhat awkward VTG (variable torque generator) was surprisingly varied and helpful.

m;

If you have separate solenoid valves for the AGR (Abgasrückführung - exhaust gas recirculation) and VTG (Variable Turbine Geometry) systems, try swapping them. If you then experience jerking or excessive soot, disconnect the electrical connection to the AGR valve (effectively turning the AGR system off).
If the boost pressure problem disappears, then in 90% of cases, you only need a new N75 valve.

Okay, it's not the N75 either; I just replaced it.

@dieselmartin

Quote:

Driving on the Autobahn in a car with an ASV (adaptive speed and distance control) that also had a somewhat clunky VTG (variable torque generator) was surprisingly varied and enjoyable.

Please explain?

Therefore, it can only be due to the turbocharger or VTG (Variable Turbine Geometry).
There's nothing I can do; I guess I'll have to take it apart and clean it. Thanks for your help. I'll let you know how it goes this weekend.

Greetings.

KANE326 wrote:

Therefore, the problem can only be due to the turbocharger or VTG (Variable Turbine Geometry).

A blocked or kinked external pressure line is also a possibility, see https://community.dieselschrauber.org/en/viewtopic.php?t=3101.

ah.. thank you, that's right. Good idea .

It wasn't the external pressure line... it seems the turbo is the only thing left.

KANE326 wrote:

@dieselmartin Quote: Driving on the Autobahn in a car with an ASV (adaptive speed and distance control) that also had a somewhat clunky VTG (variable torque generator) was surprisingly varied and enjoyable. Please explain?

Initially, I used VCDS to ensure I didn't push the boost pressure too high. Once I confirmed it stayed within acceptable limits, I drove a lot on the highway (because I had to), and unlike my usual driving style, I frequently accelerated significantly. This meant the VTG (variable turbine geometry) was constantly working hard.
This "unnecessary heating" then made the VTG system usable again.

The VTG (Variable Transmission Gear) probably got stuck on this car because it had been sitting for a year before the purchase.
To put it bluntly: completely stuck.

It's more likely to be firmly attached to you - and that might NOT be something that can be removed by scrubbing even more.

m;

Sure, here is the translation of the text from German to English:

"Addendum:"

It was actually caused by a stuck valve. I removed the turbocharger, disassembled it, cleaned it, and reinstalled it. -> It's running now.

Okay, well, you don't actually have to remove the driveshaft. You just need to loosen the pendulum support, then use a pry bar to lever the engine forward, and wedge a piece of wood somewhere. TA-DA: The turbo comes out from underneath!

Greetings.

Thank you for the clarification .

Did you also have any rust forming under the glass that sits below the VTG (vehicle tracking device)?

klahaui wrote:

Did you also have signs of rust ....

Or even photos of the turbo, disassembled, before and after...

m;

What do you mean by "disc" on the turbo?

I only took these pictures (see attachment).