TDI 81kW: Reduce Soot Emissions

Hello,

I have a Skoda Octavia with an 81 kW (110 hp) engine (license plate: ASV 071 438).
The engine has currently run approximately 86,000 km, of which about 80,000 km were with engine control unit tuning. Until a few months ago, there were no signs of the tuning, such as smoke. Two months ago, the mass airflow sensor (MAF) failed on this vehicle. Because the car wasn't consuming an excessive amount of fuel and didn't have any other 'side effects' besides the loss of power, I drove about 4,000 km further (vacation and work-related trips), as advised by a Skoda workshop (I was traveling in Belgium at the time), to have the MAF sensor repaired in Hamburg at my regular workshop, utilizing the extended warranty.

Since replacing the mass airflow sensor (MAF sensor), the engine has been producing significant plumes of smoke when accelerating, especially when downshifting and accelerating through the gears. There are no unusual 'clouds' of smoke visible during startup, etc. Under heavy load (towing approximately 1.5 tons), a small, persistent 'puff' of smoke can be seen. The driving performance remains excellent, and the fuel consumption is low. The oil consumption is approximately 0.5 liters every 3,000 km, which is also acceptable.
In the current mandatory technical inspection (AU), I unfortunately failed because of the particle emissions during the exhaust test.

Could it be that my engine oil (Longlife) has become too old (too thin) after 8 months and 26,000 km? (Suggestion from the Dekra inspector).
Could the intake manifold or another component have been damaged during the installation of the mass airflow sensor, without the computer registering any error codes in the diagnostic memory?
...
My workshop now says: with tuning, we will not search for the error under warranty.
What else could it be?

Greetings from a newbie, who's a bit lost!

Jan.

'Soot always indicates insufficient or inadequate boost pressure. Check the variable geometry turbocharger (VTG) to see if it's operating smoothly, and inspect the intake air path for leaks.'

I would also consider reversing the tuning modifications. Perhaps the black smoke you're seeing is only noticeable because of the faulty mass airflow sensor.

Otherwise, the search function should provide you with enough reading material and diagnostic options.

Soot always indicates a lack of or insufficient boost pressure. Check the VTG to see if it moves freely, and inspect the intake air path for leaks.... Thank you for the quick response.
There's plenty of power available, so it probably isn't due to a lack of boost pressure. However, I'll check it out tonight.

I would also consider reversing the tuning modifications... perhaps the black smoke was only masked by the faulty mass airflow sensor...
Unfortunately, I don't have a second control unit lying around. The 'flags' were NOT present, which I've confirmed multiple times by checking with subsequent cars. After the tuning, I was worried about whether it would be visible from the outside. Now, you can even see the 'swirls' through the rearview mirror!

Otherwise, the search function should provide you with enough reading material and diagnostic options...}
Thank you for the tip, I already did that before registering in about two weeks. However, for example, I don't have enough test equipment available. Unfortunately, I haven't been to a skilled mechanic in a long time, but rather to a large workshop because of the company car.

I will definitely keep that in mind once I have a general idea of the direction I'm heading.

Best regards,

Jan.

The oil consumption is approximately 0.5 liters per 3,000 kilometers, which is also acceptable.

Well... it's 4 times as much as my ALH needs.


Could it be that my engine oil (Longlive) has become too old (too thin) after 8 months and 26,000 km? (Suggestion from the Dekra inspector).

The previous oil analyses have actually shown that the oil tends to become thicker with increasing mileage due to the Russian loading.


Could the intake manifold or another component have been damaged during the installation of the mass airflow sensor (MAF), without the computer registering any error codes in the diagnostic memory?

Yes, that's quite possible.
Take a look at the vacuum hoses and all the stuff around them.
Possibly the AGR (Abgasrückführung) valve is sticking or a hose has burst.
'Who knows where the Klingons have been causing trouble...'

CU Gremlin.