Golf 3 TDI 1Z engine cuts out at high RPM

Hello everyone,

I have a Volkswagen Golf 3 TDI 1Z with approximately 240,000 kilometers on the odometer.
The problem is as follows:
Starting at an engine speed of 3,500 - 4,200 (depending on the model), the engine completely cuts out, and a cloud of black smoke billows from the exhaust. The warmer the engine gets, the worse it becomes. It's as if someone suddenly steals the turbo boost. If you suddenly accelerate, it will also stall (but it will emit white-gray smoke instead of black smoke) at around 4,000 RPM, and it will take a long time for it to run smoothly again. If you accelerate slowly, it will rev cleanly up to the redline.
We've already tried quite a few things, but unfortunately, none of them have worked.
Wastegate valve replaced, no success.
Turbocharger completely inspected (including wastegate linkage): OK.
Funding paused, including replacement of timing belt, no success.
Head gasket needs replacement due to oil leakage, no success.
'A new control unit was installed because the diagnostic system occasionally reported an error code related to the intake manifold pressure sensor, indicating a short circuit to positive. Unfortunately, this did not resolve the issue.'
All the injectors open at a pressure of 178-180 bar.
According to the VW diagnostic system, I have approximately 2.4 bar of boost pressure.

I'm stuck, does anyone have any other ideas?

Best regards, Arne.

Have you ever deactivated the AGR (Abgasrückführung) system using a mechanical method (also known as a metal gasket)?

CU Gremlin.

Have you ever checked or replaced the needle lifter?
It's an old 1Z problem.

Best regards, TD.

2.4 bar charging pressure???

The 1Z cannot measure that.

Where did you get this value from?

m;

'My ALH does the same thing...'

is just the ABSOLUTE pressure
After subtracting the atmospheric pressure, only 1.3 - 1.4 bar remain, which corresponds to the overshoot during the initial adjustment.

CU Gremlin.

@ Gremlin

I understand that, because:

Absolute pressure is not the same as boost pressure!!!
And "Überschwinger" are something else entirely.


I just asked because a remote diagnosis becomes even more difficult when it's based on incorrect or incomplete data, which is already a challenge in itself.

Arne should tell us what the boost pressure (target is approximately 0.9 bar) and overboost levels are. (I find 1.4 bar to be quite high for overboost!).

m;