Boost Pressure Problem: VW V6 TDI Diagnosis

Hello there,

I have a V6 TDI (AKN) engine with 120,000 km and a performance box. Unfortunately, it's a bit too smoky for my taste. That's why I was thinking about increasing the boost pressure by about 0.2 bar. Using VAG Com, you can see the target and actual values; it starts to adjust nicely around 1700 rpm, reaching 2050 mbar.

Yesterday, I installed an analog LDA (Linear Density Analyzer). But now I'm noticing that there's a pressure drop of about 0.2 bar across the entire range. The gauge settles at 0.85 bar. A second pressure gauge shows the same result. The measurement point is on the housing of the shut-off valve, where the 'faulty' EGR (Exhaust Gas Recirculation) system is connected. The actual power output might be higher than usual, but that's always been the case.


What would you do? Would you buy a new sensor, or try to jury-rig a circuit?

Or am I making a mistake in my thinking?

Thank you very much for your valuable input.

Rainer.

Hello Rainer,

A VAG-COM log showing the boost pressure and air mass readings over a wider RPM range would be helpful. A photo of the MAP sensor (Manifold Absolute Pressure sensor) afterwards might also be useful to get a better understanding of the situation.

Hello Marco and team,

I just logged in again today.

At the maximum value shown in Image 2 (2132), the pressure gauge only reads 0.9.
So, it's about a 0.2 bar deviation, and at 0.5 bar, it's only about 0.15 bar.

Does cleaning actually help? What's the best way to access the sensor on an Audi A4?



See you later, Rainer.




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Hello,

I have to ask a really silly question: shouldn't the value '2132' from VAG COM mean 2.132 bar? Then 0.9 wouldn't even be half of that??

Best regards, Manuel.

Manuel V wrote:

... I have to ask a really dumb question now, shouldn't the 2132 from VAG COM mean 2.132 bar ?

That's correct, but after subtracting the ambient air pressure of approximately 1 bar, that results in around 1.1 bar.

The engine control unit (ECU) doesn't measure overpressure.

It's me again.

Has anyone ever experienced anything like this before?

I've decided to try some sensor manipulation tomorrow.

I seem to have a 3-wire sensor; which method is the best?

After struggling with the search function, I think I'll drive the sensor output with a diode. To achieve the required current flow, I need a resistor of 10-20 kΩ connected to ground.

With a voltage drop of 0.5V, I should get 0.1 bar more pressure than the standard value (since I'm currently short by 0.2 bar). Let's see if this holds true in practice.

Who among you has had any experience with this?

Thank you, Rainer.

Hi fellow namesake,

If your measured value is correct at 0.85 bar and the display is working properly, then something is broken. In that case, I wouldn't waste time trying to fix it with other boost pressure sensors; instead, you should focus on fixing the underlying problem.
What do the measurement blocks in the engine control unit say regarding the atmospheric pressure readings?

Best regards, Rainer.

Hello Rainer,

Yes, I also think the boost pressure sensor is faulty. When you turn on the ignition, both values are close together, but then they diverge, with one reading up to 1 bar while the other reads 0.2 bar.

I was planning to get a slight boost in performance anyway, so I installed a diode today. Now I have about 1.2 bar of boost pressure. But in the long run, I'll need to look into getting a new sensor.

Does anyone know how much one of those costs?

This is printed on my Bosch 0281 002 326 VAG 059 906 051.

On this Russian website, I found the price of 038 906 051 (which is mine) listed for $80.
and 038 906 051 B (40$) for a 2002 model.

Does anyone know what the difference is between a 051 and a 051B?

Thank you in advance.
Rainer.

Hello Rainer,

"Although your post is quite old, I have two questions:"

Do you know what thread the hole has at the EGR inlet where you connected the LDA?

- What does the throttle valve do when the EGR system is closed? Does it try to artificially lower the mass airflow sensor reading by closing?

Best regards,
Albrecht

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.

ok, M8x1 thanks.

Is there any further information available regarding the disposal code (DK) for a decommissioned agricultural land (AGR)?

Best regards,

As far as I know, a throttle valve was only introduced with the Euro4 engines; before that, it was simply a shut-off valve.