Boost Pressure Fluctuations

Hello, I'm new to the forum. I'm from Denmark, so I might not always use the correct word for some parts.
I'm experiencing fluctuating boost pressure, just like others.
I recently bought an Audi 80 Avant TDI, but I'm having a problem with it. When I accelerate fully, I can hear the turbocharger spooling up and then winding down again, which is also noticeable in the performance. I replaced the mass airflow sensor (MAF), but that didn't help. The pressure sensor on the wastegate seems to be working correctly, and the magnetic valve is receiving 12.3V. I even removed it and checked it; it clicks and opens and closes when I apply 12V.
'Today I connected a pressure gauge to the intake manifold. When I give it gas, the boost pressure briefly rises to 1-1.2 bar, then drops to a stable 0.8 bar for a short time. Then I feel small, rapid vibrations, which I think is normal. However, at the same time, the boost pressure starts fluctuating between 0.2-0.3 and 0.8 bar.'

The engine is a 1Z.

What should I do now to find the error?

Best regards.

Henrik Lyck.

Hello,

Is the wastegate adjustment easy to operate?

Yes, I unscrewed the pressure sensor from its bracket and everything came off easily.

Henrik Lyck wrote:

What now, how do I proceed to find the error?

Connect the pressure hose directly from the intake manifold to the turbocharger housing.
If the pressure is then set to a constant value of approximately 0.6 bar, the turbocharger is working correctly.

Then check the thin hoses or replace the solenoid valve.

Okay, I'm ready. Please provide the German text you want me to translate into English. Just paste it here, and I will give you the translation.

I just tried the test mentioned above. The charging pressure is about 0.6 bar, and the vibrations are still present, but that's probably due to the intake system.
The charging pressure is now constant. I already replaced the thin hoses a week ago. If the solenoid valve is working as I described, could it still be defective?

Henrik Lyck wrote:

The charging pressure is now constant... if the solenoid valve works as I described, could it still be defective?

Probably yes, but that's something that 1Z practitioners should comment on...

In the solenoid valve, a small metal bolt with rubber ends moves back and forth inside a cylinder. If a foreign object gets through, the rubber ends can easily break, which compromises the seal. Additionally, oil tends to accumulate in the solenoid valve. I would replace this part, especially since it's not that expensive when bought in Germany (about 32 Euros). In Denmark, it costs almost three times as much! (approximately 650 DKK = 86 Euros)
There are now some Volkswagen dealerships that ship cheaper parts to Denmark, which typically saves around 50%.

/Jan

Okay, thank you for your help; hopefully I can find the error.
Does a practitioner of 1Z have any comments?
By the way, the engine has an EGR system.