2.0 TDI BMM: Power Loss, Soot & DPF Issues

Hello diesel enthusiasts,

I'm new here and I'm already posting about a problem. Unfortunately, I couldn't find any relevant results using the search function. So, I'll try to describe it as accurately as possible.

I drive a Skoda Octavia Scout with the engine code BMM, which is a 2.0L TDI common rail diesel with 8 valves.

Regarding the car's history, it was purchased with an engine problem (a connecting rod failure at 190,000 km), and we subsequently installed a rebuilt engine. At the same time, the common rail injectors were sent for inspection and refurbishment, and a new DPF (diesel particulate filter), new glow plugs, and a new wiring harness for the common rail system were also installed.

However, problems with regeneration continue to occur. Because it was regenerating prematurely due to some short trips, I tried to initiate a forced regeneration cycle without success. There were no other error codes stored in the system. Eventually, we realized that it would regenerate at higher engine speeds, specifically around 3000 RPM. During further troubleshooting, we replaced the temperature sensor after the turbocharger because the readings were not entirely consistent, and we also replaced the differential pressure sensor.

All turbo hoses have been replaced, the mass airflow sensor is functioning correctly, and the turbo control system is also working according to the "actual vs. target" comparison.

Bei Kurzstrecken kann man der Rußmenge beim Wachsen quasi zuschauen, teilweise kommt es bei weniger als 50km schon zu einer Regeneration. Auf längeren Strecken gibt es dieses Problem nicht. ALet's talk about the AU.
When we inserted the measuring device, we naturally observed a turbidity value that was far too high.

After the engine was broken in, it also turned out that, in my opinion, the full power is not being delivered, and the engine makes an excessively loud "knocking" sound. Furthermore, the fuel consumption of 7.5-8.5 liters on long distances seems high, and even more so on short trips, which I don't consider normal.
The oil consumption is low and still within an acceptable range, but I think the turbocharger will be installed soon.

My last idea would be to go with the PDE again, or perhaps there's a reason why the start date of the funding isn't aligning.

So, to summarize and reiterate the problems:
- excessive fuel consumption
- insufficient performance.
- too loud running noise.
- It doesn't start as easily when the outside temperature is cold.
- Regeneration is only possible at 3000 RPM.
- excessive soot formation.

I really don't know what to do anymore . I hope you can help me.
If you need any further information or excerpts from diagnostic reports, please just let me know what you require.
Thanks in advance, and have a great start to your week!

Hello and welcome.

Have you checked the valve timing yet?

Regards,

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Please provide the "Autoscan" and "synchronization angle" values from the engine control unit (ECU) readings.

Best regards, Rainer.

Hello,

"I haven't checked the valve timing yet, that's a good idea. Just out of curiosity, at what difference between the camshaft and crankshaft would the engine control unit detect a misalignment? Is it possible to give a general answer to that?"

I have attached the auto-scan results, a log file, and a diagram. I hope I did everything correctly.

Best regards,
JavaScript.

Without having read it in detail, I see a rotation angle of -2 degrees. I can't imagine that the control unit would malfunction before there is physical contact between the components.

I would check the valve timing; it's a quick process.

Hello,

What is the DPF fill level or differential pressure?

Sure, here is the translation of the text from German to English:

"Background information:"
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Best regards, Rainer.

Thank you very much for your answers. Finally, I managed to investigate further, and here's the next update:

- Valve timing has been checked and is correct.
-> The rotation angle still fluctuates between -1.5.
and -2.5 degrees.
- The preconditions for the PDE were also rechecked.
- I have attached some pictures regarding differential pressure, etc.

Ich hatte jetzt die Überlegung, ob es vielleicht unterschiedliche Kurbelwellen-Zahnräder gibt, da ja mal ein Austauschmotor verbaut wurde. Nockenwellenrad ist sicher vom BMM. WAre you eating more there?

Unfortunately, I don't have any log files, only screenshots, because I saw the links too late. There are three screenshots: one showing the system at idle, one under full load, and one showing the DPF loading status.
-Ambient air pressure was approximately 980 millibars.
- Temperature: 5 degrees Celsius.
- DPF replaced 5000 km ago.


Best regards,

Does anyone have any other ideas?
I'm just going around in circles.

Why don't you read my links and answer the question that was asked?

Where does the ash mass of 0 come from in the Screenshot, Santa Claus?

I can certainly perform a pressure difference measurement related to the DPF, but it's just a snapshot in time. When the DPF has been recently regenerated, the pressure difference at idle is approximately 2 mbar. However, as soot builds up and under full load, this pressure difference can increase to around 370 mbar.

Based on the apparently large amount of soot and the high turbidity value indicated by the AU tester, I suspect that the engine is simply producing too much soot.

Just to go back to the crankshaft angle: how can it be that the crankshaft angle is -2 degrees despite having correct timing?

I can't say where the ash mass value for the DPF comes from. The value isn't increasing, and even when manually entering it via VCDS, it doesn't show a higher value.

JS1 wrote:

Just to go back to the crankshaft angle: how can it be that the crankshaft angle is -2 degrees despite having correct timing?

What does "appropriate valve timing" mean?
If the timing is set perfectly accurately, you'll have a rotational angle of 0°. However, if you just replace the timing belt according to the workshop manual, it can easily be off by 1-2° plus or minus. I worked carefully and even after the replacement, I wasn't exactly at 0°. (For other reasons), I removed the timing belt again and repeatedly tensioned it (using a locking tool), rotated the engine, etc., until the locking tool just slid into place on the crankshaft and camshaft sprockets. Afterwards, VCDS showed 0°.

Correcting the steering angle is a quick process with VCDS, and you don't have to disassemble much to do it. You'll also see how small the range of adjustment is.

Best regards, Tobias.

Hello,

Perhaps you could try removing the DPF and see if the engine produces visible exhaust smoke while driving. If it does, what color is the smoke?
Have you checked if there's a tuning module or similar device installed? Is the engine control unit software definitely original?

Best regards, Rainer.