1.9 TDI AHF: Power Loss in 5th Gear at 3600 RPM

Hello, it's me again.
with a new alarming message.
When accelerating the vehicle, everything runs smoothly, and I can rev the engine up to 4200 RPM in all gears up to 4th. However, in 5th gear, it starts to bog down at 3600 RPM and only slowly reaches 4500 RPM.
During a test using the diagnostic tool, I noticed that the lever on the vacuum actuator of the turbo only moves a few millimeters. According to the Bosch hotline, it should move at least 15 millimeters. My boost pressure is consistently at 0.95 bar. Is it really the actuator, or is there another explanation for this?

As always.
Thank you very much for your help.

Dieselmike.

Dieselmike wrote:

During a test with the diagnostic tool, I noticed that the lever on the vacuum actuator of the turbo only moves a few millimeters, but according to the Bosch hotline, it should move at least 15mm back and forth. My boost pressure is constantly at 0.95 bar.

In my opinion, these things don't go together.
With a very limited adjustment range of the VTG (Variable Turbine Geometry), it is not possible to maintain a boost pressure of 0.95 bar across the entire engine speed range.

Did you perhaps run the test with the engine running? If so, the vacuum in the reservoir will be used up, and after a few cycles, the device will only work weakly.

Hello Ulf,
I performed the test with the engine running and at idle. Even when accelerating, the boost pressure remained within the range of 0.91 to 1.04.

Best regards,
Mike.
desperate

Dieselmike wrote:

Hello Ulf. I performed the test with the engine running and at idle. Even when accelerating, the boost pressure remained within the range of 0.91 to 1.04. Best regards, Mike. desperate

Hi, your test is useless. This is not how boost pressure is measured. For a stationary car, i.e., without load, it's far too high, which also explains the error.
Starting around 3 seconds of full throttle in a high gear, the boost pressure should settle at approximately 1 bar if the boost pressure control system is functioning correctly.

Best regards, Rainer.

Rainer K. wrote:

Dieselmike wrote: I performed the test with the engine running and the vehicle stationary. Even when accelerating, the boost pressure remained within the range of 0.91 to 1.04. Hi, Your test is useless. It doesn't measure the boost pressure correctly. For a stationary car, meaning without any load, the reading is far too high, which also explains the error. Starting at approximately 3 seconds of full throttle in a high gear, the boost pressure should settle at approximately 1 bar, if the boost pressure control system is functioning correctly.

Hi Rainer and Mike,

Okay, I honestly don't see much of a way to generate a boost pressure of around 1 bar (relative!) under normal operating conditions – except maybe during a dyno test, where the pressure briefly spikes up in that area.

At 1 bar relative pressure, within the idle speed range, using a standard TDI turbocharger, Garrett + Co would likely be very interested.

Have you had the boost pressure read? Then 1 bar would be the absolute pressure, which is normal when the engine is idling and tells you practically nothing - except that the intake path is not severely blocked.