Audi A6 2.0 TDI PD, DPF regeneration every 50km + smoke emissions

Good morning, everyone.

After reading many threads on the topic of DPFs and everything related to them over the past two weeks, I would like to describe my specific problem in detail and hope that with your help, I can get closer to a solution.

Problem:
1. Regeneration approximately every 50 kilometers.
2. The vehicle is emitting a lot of smoke during regeneration, and it smells like fuel.
3. The vehicle jerks and runs unevenly during regenerative braking.
4. The engine oil smells like exhaust fumes (smelled near the oil filler cap).
5. Oil proliferation.

Under normal operating conditions (not during regeneration), the car appears to be running well. It has good power, with no noticeable jerking or unusual noises. In my opinion, the performance decreases somewhat, even up to the point of regeneration (around 50 km).

A check with VCDS showed that the differential pressure, which was 30 mBar (under load - freshly regenerated), steadily increased to 323.85 (under load) during the 50 km until the regeneration process started. The regeneration process ended after approximately 8 km, with appropriate driving (1800 RPM, 4th gear, approximately 60 km/h). Differential pressure then returns to 2.5 mbar (idle) or 30-40 mbar (load).

To me, it looks like the DPF is clogging up extremely quickly. This is either because the DPF is of poor quality, or because the engine is producing an excessive amount of soot. I haven't been able to figure out which of those things is actually true yet.

My next guesses are pointing towards the power distribution (PD) components or the PD wiring harness. Before I replace them, I would still check the compression. The lid is already open anyway .


Background:
Approximately 3 weeks ago, the vehicle went into emergency mode. The car was driven for a few kilometers (~20) in emergency mode before it completely shut off. If I remember correctly, error codes related to the EGR valve, DPF, and low boost pressure were stored. After the EGR valve was replaced (with a VDO Siemens unit), the car ran for a short time, but it didn't develop any power and then shut off again. It turned out that the DPF was completely clogged. So, it was also replaced (with a DPF from China for 200 EUR). In addition, the differential pressure sensor, mass airflow sensor, air filter, and fuel filter were replaced.


I hope this information is helpful. Of course, I can provide corresponding VCDS logs if needed. Just tell me exactly what you need.


Best regards from Rheine.
Michael.

Please run a diagnostic scan to see what errors are currently stored.

"China DPF" sounds suspicious...

Hello,

Located in the front right, behind the bumper, there is an "air cooler" in the charge air duct. Please check if its connection to the intercooler is airtight.
Leaks often reveal themselves through oil stains.

Please provide a full-throttle log with engine speed (RPM), actual air mass, target boost pressure, and actual boost pressure, covering the range of 1500-4000 RPM.
Don't forget to enable the Turbo mode when logging or grouping measurement values, so that the temporal resolution is usable.

Best regards, Rainer.

Please find the Autoscan file attached.

Here is the log file.

Hi,

Based on both the actual air mass values and the charge pressure control, it doesn't appear there's a significant leak in the charge air system.

What value do you see for the differential pressure at the DPF when the ignition is on but the engine is off?

What ash mass value did you set in the engine control unit after replacing the DPF?

What is the current ash mass reading that the engine control unit (ECU) sees? (This should be measurement block 68.)

According to your mileage, the drive mechanism of the oil pump in the engine should already be defective. Who repaired it, and how?
Translation:

Background: Without oil supply, the bearing in the turbocharger will quickly become damaged, which then leads to oil consumption with smoke and causes the DPF (Diesel Particulate Filter) to clog rapidly.

Best regards, Rainer.

Hi,
I repeatedly observe a lag in the boost pressure, both when accelerating and decelerating.
While it may not seem relevant to the current problem, isn't this an indication of a pending VTG (Vehicle Train Graph) update?
What surprises me: The vehicle is smoking during regeneration (and smells like diesel) - despite having a DPF?!
I could understand that if there were no DPF.
hg
Herbert.

Hi.

Herbert wrote:

Hi, I repeatedly observe a lag in the boost pressure, both when accelerating and decelerating. For the current problem, it doesn't seem relevant, but isn't that an indication of a pending VTG?

Yes, it seems acceptable, although the VTG (variable transmission gear) might be slightly dirty, but it's not a VTG-related issue.

I had to replace the AGR valve and throttle body several times in my car, but I was able to do so affordably by using compatible parts from the aftermarket.
Possible causes for the rapid DPF filling could also include issues with the AGR system, but in my case, the error light and limp mode came on immediately when the problem occurred. Voluntarily, you won't be able to travel very far with only what feels like 50 horsepower.

Best regards, Rainer.

Again

Quote:

What surprises me: The vehicle is smoking during regeneration (and smells like diesel) - despite having a DPF?! I could understand that if there were no DPF.

Would a functioning or tightly sealed particulate filter allow smoke to pass through? And wouldn't the fuel have to burn inside the DPF?
hg
Herbert.

Quote:

Would a working or dense particulate filter let smoke through? And the fuel should be burned inside the DPF, right?

Good question... However, when I regenerate, I don't smell violets either, and I don't experience any problems.

Possibly check the idle speed control for any anomalies (measurement block 13).

Best regards, Rainer.

Hello everyone,

Okay, I'll try to answer the questions in order.

Rainer:
1. Diff. Engine pressure: 0.00.
2. The ash mass value cannot be entered. I tried to adjust the hexadecimal value for 5g in the long adjustments of channel 12. However, nothing I enter is accepted. Ash value always remains at zero (Am I doing something wrong?)
3. Ashmass remains at zero.
4. To my knowledge, the oil pump has not yet been repaired.

Herbert:
"When I keep the engine at an idle speed of 1500 RPM in regeneration mode, I experience excessive smoke. This also happens during driving in the load change range. As the load and RPM increase during acceleration (not full throttle), the smoke decreases..." I'm posting a Screenshot of MWB 13.
I also saw that he administers an additional 20mg/hour during the regeneration process. Does the amount seem right?

Rainer:
AGR is new and is a brand component. The throttle body has been cleaned. I also don't have any errors in the ECU.


By the way... The MWB 18 magnetic valve status shows 128 when I release the accelerator pedal while driving. As soon as I press the accelerator, the "128" disappears.

Hi,

Ash mass is 0, okay. Idle speed control values are normal.

What about the oil level? Does it remain the same, or does it decrease slightly when the engine is running?

Is the engine unmodified, and is there no tuning box available?

Your engine has an oxygen sensor in the DPF. Please provide a full-throttle log of the values from 1500 to 4000 rpm.

Best regards, Rainer.

Hello Rainer,

I will send you the lambda values shortly. Thank you very much for all your wonderful support so far! (To everyone)

I'm currently wondering if it could be due to a China-made DPF. After some research, I found that the honeycomb structures are usually significantly "smaller" and have a completely different flow/filtering behavior compared to the expensive original parts. If the DPF is removed and the vehicle goes into regeneration mode (without the DPF being deprogrammed from the control unit), it should also cause significant smoke emissions because the injected fuel can no longer be (completely) burned in the DPF. That at least sounds logical, I think.

Specifically:
Has anyone experienced a regeneration cycle without a DPF, and can they confirm the "smoke theory"?

Best regards,
Michael

roetty wrote:

I'm currently wondering if it could be related to the China-DPF. After some research, I found that the honeycomb structures are usually significantly "smaller" and have a completely different flow/filtration behavior compared to the expensive originals.

It's not about China or non-China. You have no more reference point. Because this DPF is almost certainly not built to the original specification. And therefore, this fact alone may be sufficient to cause a system failure.

Question: How does the display value of the DDS behave? Does this display the absolute pressure difference, or is the displayed value calculated based on the ash mass?

The reason for my question is: After replacing the DPF, I couldn't set a value for the ash mass; only "NULL" was possible. If the DDS value depends on it, that could be a possible explanation for the frequent regeneration, right?

Best regards,
Michael

Hi.

The differential pressure sensor displays the measured value, and if the "rest value" is correct, then it should be working properly.

Is the correct differential pressure sensor installed? The high pressure differences could theoretically be caused not only by excessive Russian loading, but also because the wrong sensor with an incorrect measurement range is being used.

See:
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Best regards, Rainer.