2.5 TDI: Better After MAF Sensor, But Not Perfect

Hello everyone,
It's only partially true: Yes, I signed up here because of the high technical level, but not just that. I've never dealt with people who also have a good sense of cars. No, I'm serious. When I tried to share my impressions about the workshop, I quickly realized that the guys there usually couldn't follow me, or didn't want to. My A4 B5 2.5 TDI AKN is my first "better" car, and it was love at first sight. I've only had it for 3 weeks, but due to my lack of experience and probably also because of a blinding effect, I'm slowly realizing that it's not running as well as it could. And despite the quirks, I'm happy every time I need the car.

My previous experience with diesel cars includes a 2.0 Astra with 100 horsepower (150,000 km) and a few kilometers in a 90 horsepower Golf TDI. With both cars, I found that if you were driving, for example, at 50 km/h in third gear in a town, just before the turbo kicks in fully, and then gave it, say, 50-60% throttle when exiting the town, you got the best acceleration. A similar principle applies when preparing to overtake a truck. In my experience, full throttle would have less of an effect. This also applies to gasoline engines, with the exception of the new turbocharged gasoline engines from VW. However, I'm not entirely sure about that.

Nun zum AKN in meinem B5. Zuerst dachte ich, der 6Zylinder hat einfach ne andere Charakteristik, aber bei häufigerem hineinfühlen wurde es immer deutlicher, dass der Motor bei ca 2000 RPM ganz kurz den typischen Dieseldruck andeutet, dann aber etwas müde hochzieht. Ich habe nachgeforscht und den LMM getauscht. Ja, das fühlte sich schon besser an. Nachdem ich ihn ein paar km auf der Autobahn geheizt habe, war nochmals eine deutliche Verbesserung zu spüren. Es kam fast an das heran, wie ich es eigentlich erwarten würde. Der Fehlerspeicher ist übrigens leer. Nun ist es so, dass es jeden Tag mal besser, mal schlechter ist und wirklich zufrieden bin ich nicht. Die beste Beschleunigung erhalte ich mit einem genau angepassten drücken des Gaspedals, was aber nicht immer klappt. Die alte Taktik, 50 - 60 % Vollgas geht nicht wirklich auf, zu viel Gas verlangsamt die Beschleunigung. Zum freundlichen will ich erstmal noch nicht, denn als ich Hilfe beim LMM brauchte wegen der verdammten 5-Stern Torx Schraube mit Stift, war der Mitarbeiter dort eigentlich gleich bereit mir ohne Auftrag zu helfen, sagte aber dann, als er sah, dass ich nur den Sensor habe, dass das nicht ginge, weil der genau im Luftstrom sitzen müsse und dazu müsste ich das ganze Trumm mit dem Rohr haben. Nun hab ich die Schrauben mit ner Wasserpumpenzange raus und dabei festgestellt, dass das absolut idiotensicher ist, denn weder kann man den justieren, noch falsch einbauen. Soviel zum freundlichen. Ich hör jetzt schon, was die austauschen wollen, was sich vielleicht günstiger lösen lässt. Zur Höchstgeschwindigkeit kann ich nicht wirklich was sagen, dazu hab ich ihn zu kurz, 220 lt. Tacho gehen aber schon. Ach, It has 140,000 km on the odometer.

Okay, so the cat's out of the bag. I'm an interested amateur. I know some things, but obviously not everything. Maybe someone has a valuable tip, based on the information that the "full throttle" approach (presumably referring to a specific setting or procedure) brought a significant improvement, in addition to replacing the mass airflow sensor.

Best regards and thank you in advance.

I saw.

mhh...

I'm still not entirely sure where the problem with your engine lies. Regarding the mass airflow sensor (MAF): Where did you buy it, and how cheap was it? Was it one of those cheap things from eBay? If so, you probably won't have much luck with it.
It's perfectly normal for a 6-cylinder engine to have a completely different characteristic compared to smaller 4-cylinder engines.
Have you already read about the AKN engine and its problems, which typically start around your mileage, using the keyword "camshaft"?

Hi,

"That was the Pierburg LMM (mass airflow sensor) from the auto parts store, costing 86 Euros. I really hope it's not something else expensive, like a problem with the engine internals. I couldn't afford that. Otherwise, the car is very quiet and smooth. There's no smoke or any kind of jerking."

"With a 6-cylinder engine, you automatically tend to drive at lower RPMs, at least that's my experience. It pulls cleanly from 1600 RPM, while a 4-cylinder engine still sounds strained and isn't very responsive. The AFB/AKN engines are a bit stiffer than the 4-cylinder engines and don't rev up as quickly. I see these engines more as being suitable for a delivery van than for a race car. However, they don't run out of breath as quickly as the 4-cylinder engines; they rev cleanly and powerfully up to 4500 RPM, although they don't feel quite as comfortable at that level."

It's possible that the VTG (Variable Turbine Geometry) is sticking slightly and not always functioning 100%, which means it might not build up full pressure. This can lead to less air mass being detected, and the fuel injection amount might be reduced. You'll likely see this in the near future. I can confirm what you said about the highway driving; after the vacation, mine runs noticeably better than it did after months of driving in heavy traffic on small roads.
These are my experiences.

See you later.