It took some time, but the problem is solved! The patient is walking again!
But I don't want to end this topic without a summary, as it would certainly be helpful for those who have experienced something similar!
After I've been dealing with the particulate filter issue, extremely increasing soot buildup, continuous regenerations, and exorbitant differential pressures on the DPF for quite some time, everything is now back to normal.
No debugging without learning, I'm now smarter!
Not always is the particulate filter the culprit, if regeneration is triggered too frequently. The differential pressure sensor actually only measures the counter-pressure in the entire exhaust system. The control unit assigns a soot loading value to the differential pressure and initiates one of the three DPF regenerations depending on the resulting soot mass.
First, the field regeneration:
This is initiated when the soot mass reaches 22.53g. If the vehicle is switched off in between, the regeneration process is immediately initiated upon each restart. By increasing the fuel input, high exhaust temperatures are generated within a few meters/minutes, allowing the soot to burn.
If you frequently shut down the engine during short-distance operation, you will quickly encounter the problem that the next regeneration phase will be reached.
Secondly, service regeneration:
This is introduced with 40g of soot mass. If this is done too often, the DPF light will come on and instruct the driver to perform a regeneration cycle according to the manual.
As the third option: Forced Regeneration:
If the soot mass exceeds 50g, the DPF is considered overloaded. The control unit will no longer initiate a regeneration, and the only solution is to use VCDS and have a fire extinguisher nearby.
In my case, I assumed that the DPF was simply full and worn out after 200,000 km. Therefore, it was replaced with a new part. However, the subsequent test drive unfortunately did not show any better soot loading values. Within 10 minutes of driving at moderate speed, the loading increased from 6.96g to 24.90g. The field regeneration was initiated, but the soot loading values still increased dramatically. This, of course, also resulted in higher exhaust gas temperatures due to the after-injection activated by the control unit. The amount of soot removed was not proportional to the amount of soot added, therefore, I would have seen the DPF light again in no time with the new DPF.
By the way, the engine has not produced excessive smoke in any driving situation, and the high differential pressure has only given the control unit a false impression of excessive soot buildup, and also me!
Because I didn't believe that the new particulate filter was already clogged, I disconnected the subsequent SCR-cat from the DPF. And the result was clear: the pressure differential was within normal ranges.
Only at this stage did I hear the SCR-cat chime, as if the ceramic inside was loose within the casing.
After the expansion, it became clear. The attached image shows what I encountered.
I have found a company that also offers pre-fabricated SCR catalysts, and I have found one that is suitable for my needs. A new part was also not an option here, as I prefer repairs that are cost-effective.
A phone call with the boss was very helpful, as he was able to explain the background of the defective ceramic to me. His statements are convincing to me, and I am sharing them here without any expectation of scientific verification.
"The injected AdBlue can crystallize in certain operating conditions and thus settle into the cavities of the ceramic parts. There, the crystals act like small files under the exhaust pressure, which can damage the ceramic over time." "The mileage of your 200Tkm engine is already at the limit for the SCR catalyst!"
In light of the EA189 emissions issues and the corresponding software changes, it appears to be a complete solution. The amount of AdBlue injected was approximately doubled by VW, without any changes to the hardware.
After I had already invested 1300 euros for the DPF and the SCR-catalyst, the values are now back in the normal range, and the car is running properly.
The soot mass increases by 8g per hour of driving time over 100 kilometers in urban and suburban traffic, which, in my opinion, is a reasonable value that I can easily live with. A corresponding log will be attached.
Note… High differential pressure values are not always caused by a faulty DPF! The entire exhaust system should be checked for proper flow, as a precaution.
Greetings
Ralf
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I found the invoice still in the old documents.
