Audi A3 1.9 TDI: No Power Below 2800 RPM

Hello, I have an A3 1.9 TDI with a ******** chip. Recently, it has had absolutely no power at low RPMs, up to about 2800 RPM, and it doesn't seem to be building any boost; however, it runs perfectly fine at higher RPMs. The workshop, as expected, wants to replace the turbocharger. The boost control valve was replaced as a test, but it didn't improve anything. I just checked the pressure sensor, and it seems to be sealed. The hoses are also sealed. Now I'm at a loss! The engine doesn't immediately go into limp mode at low RPMs (which I would have expected if the turbo wasn't building boost), but only occasionally.

What percentage is displayed for the duty cycle of the magnetic valve used for turbocharger pressure regulation (after 2-3 seconds of full throttle, then read the value)?
Is the VTG adjustment common? Is the vacuum hose chewed?

Best regards, Rainer.

Hello, unfortunately, I cannot read the duty cycle myself. The hose is okay, and the VTG (variable turbine geometry) is moving freely. The VTG immediately moves to the maximum position when the engine starts, so why isn't there any boost pressure?

master_328 wrote:

The VTG immediately goes to the maximum position after the engine starts, so why isn't there any boost pressure?

Well, I guess the only solution is to use an OBD scanner (for observation) and VAGCOM, along with a lot of time, to log data until you pinpoint the problem.

Okay, I thought so... What could the problem be? Any guesses? Why doesn't the car immediately go into emergency mode if the turbocharger pressure isn't building up correctly?

master_328 wrote:

mmm, I thought so... what could the problem be? Any guesses? Why doesn't the car immediately go into emergency mode when the turbocharger pressure isn't building up correctly?

When it comes to vehicles with modifications ("chipped" cars), many things are different, and "normal" assumptions may be useless.

At some point, we discussed here the potential long-term consequences of a CT (presumably a software crash), because one vehicle seemed to be running with the standard software again after some time.