Boost Pressure Control Difference AHH

Hello,

I can't seem to make any progress with my problem on my own anymore.

Vehicle:
Passat 3B, manufactured in January 1999, 1.9L TDI, 66kW, engine code AHH.

Problem:
The fault memory indicates a difference in pressure in the turbocharger pressure control system.
When accelerating rapidly, the engine enters a limp mode at approximately 3800 RPM.
The actual boost pressure is too high!
After the engine is switched off, it continues to operate in its normal characteristic map until...
Incidentally, all this drama started after a visit to the technical inspection service (TÜV).

Previous measures:
The vacuum hoses in the system were inspected and/or replaced.
The turbocharger wastegate valve was defective and has been replaced.
After that, the car ran for approximately 5000 km without any problems until the familiar issue reappeared.
VTG rods are common and typically move about 1 cm.

I'm completely at a loss!

I have uploaded a log file to the "Upload" section.

/viewtopic.php?p=168449#168449

I would really appreciate it if one of the "Diesel Foxes" could take a look at the file and give me a general direction for further troubleshooting.

Thank you very much!

Greetings from Franconia.

Christoph.

Disconnect the vacuum hose from the vacuum sensor on the turbocharger and seal it. Then, please log data block 11 while applying full throttle.

Hello,
The log data shows that the actual boost pressure is significantly higher than the target value, yet the control system is almost fully engaged. The control system is not attempting to reduce the pressure; instead, it's increasing it until the emergency mode is triggered.
The amount of air drawn in is also related to the turbocharger's boost pressure.
Question: Is the system completely original, or has it been modified?
Sure, here is the translation of the text from German to English:

"vg"

This is a common abbreviation for "very good" in German. It is often used in online forums and chat rooms.
Herbert.

Quote:

Question: Is the system completely original, or has it been modified/tuned?

A legitimate question, however, the engine control unit (ECU) attempts to fully reduce the boost pressure, but this fails.

I probably misinterpreted the duty cycle.
Sure, here is the translation of the text from German to English:

"vg"

This is a common abbreviation for "very good" in German. It is often used in online forums and chat rooms.
Herbert.

Sure, no problem! Just provide the text you want me to translate.

It's all original and has already covered almost 280,000 kilometers in this configuration!

I'm going to try running the MWB11 without the hose connected to the vacuum sensor tomorrow.
Is it enough to just rev the engine while it's idling, or do I need to do it under load, like the blocks that have already been submitted?

Best regards, Christoph.

opal wrote:

Is it enough if I rev the engine while it's idling, or do I need to do it under load, like the blocks that were already submitted!

Under load, i.e., in 4th or 5th gear, it performs best.

Good morning.

The log for the vacuum chamber that has been decommissioned is available at the following link:

/viewtopic.php?t=23371


Best regards, Christoph[/url]

In both logs, the target LD value is significantly lower than the actual value, meaning that the 'end stop' of the VTG adjustment is being reached.

Possible sources of error:
- The VTG mechanism occasionally jams or is difficult to operate.
- Vacuum hose connected incorrectly.
- Vacuum venting system defective/blocked.
- Faulty boost pressure control solenoid valve.

For details on each point, please refer to the search function or relevant articles.

Best regards, Rainer.

Thank you for the tips.

They are essentially all positions that I have considered before, but perhaps not explored thoroughly enough.



Another question

1. - Vacuum vent defective/blocked.
If you disconnect the hose at the air filter box (where the clean air intake is located) while the engine is idling, there is a slight vacuum present. Is this normal? Because then the vacuum in the system would collapse.

If that's not the case, it would indicate a faulty solenoid valve.
Since there is a vacuum at the vent, I think a blockage can be ruled out.

2. - Faulty boost pressure control solenoid valve.
It's new, but you never know. I'll take it apart and check it out.
"This part cost 89 EUR for the AHH. Is there a cheaper alternative available? Perhaps for a different model where only the connector needs to be rewired."


3. - The VTG mechanism occasionally jams or is difficult to operate.
If options 1 and 2 don't work, I'll take another look. The VTG (Variable Transmission Gear) moves smoothly when operated with a syringe.

- Vacuum hose incorrectly connected (I'm ruling this out because it worked perfectly for a while with this setup).


I'll be in touch again!

Best regards,
Christoph.