High fuel consumption Audi A4 B6 1.9 TDI AVF

Hello everyone.

For clarity, I've created a new topic; if that's not okay, please merge it with the old one.

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

"Brief summary:"
Es handelt sich um einen Audi A4 B6, 1.9TDI Quattro, Motorcode AVF, Handschalter 6-Gang. KM Stand aktuell 369xxx, in meinem Besitz seit 248xxx. Chip-tuning wurde beim Vorbesitzer gemacht, KM Stand unbekannt. Ich fuhr den Wagen bis letzten Herbst mit einem Realverbrauch von knapp 6 Litern. Sommer wie Winter, Klima usw., kaum je ein Unterschied bemerkt. Im Herbst war der Zahnriemen fällig und gründlich wie ich bin (hätte besser die Finger davon gelassen) habe ich Zahnriemen, Spannrolle, Umlenkrolle, Wasserpumpe sowie Poly-V-Riemen inkl. Spann- und Umlenkrolle getauscht, sowie alle Filter (ausser Diesel, den habe ich zuletzt bei 337xxx gemacht). DiIt was at a mileage of 357,000 km.

Then the problems started. The average fuel consumption increased to over 6.5 liters (actual consumption; always record kilometers and liters in an app), despite a lot of long-distance driving. In city driving or short trips, I often had 10-12 liters. (The onboard computer shows this, but I'm also not getting as far on a tank as I used to, even though there's more long-distance driving now).

Checked:
- Leak tightness of the charge air system (pressure tested).
- Vacuum system
- Timing (checked and adjusted with VCDS).
- all possible temperatures.
- LMM replaced with another used unit, no change.
- Replaced the LMM with a diode, no change.
- EGR system removed, intake channels are clean (the EGR system had a metal plate installed a long time ago).

Here's what's new:
- Boost pressure sensor.
- Temperature sensor
- PD cable harness

I also adjusted the PD elements. I've now managed to get him down to a real-world consumption of 6.2 liters, but that was mostly during long drives. When I drive shorter distances, the fuel consumption increases (more than before/normally).

This week, I replaced the camshaft including the hydraulic lifters. (The exhaust valve lifter for cylinder number 1 showed clear signs of wear, but was still functioning properly).
Therefore, the change of the camshaft did not bring any improvement; on the contrary, I feel like the fuel consumption has even increased. With the same driving style as before, I'm getting an average of 7-8 liters per 10-20 km, instead of 6-6.5 liters.

Today I created some log files. Unfortunately, my engine control unit cannot record data with a higher resolution. I hope you can still find something useful in the data; I was driving in 2nd and 3rd gear. On the straight section of road, the surface was unfortunately not perfectly level, so there were slight inclines and declines.

In the BC (trip computer), I get a fuel consumption of 8-10 liters in 3rd gear when driving straight at a constant speed. When going uphill with cruise control (around 50 km/h), it's over 20 liters. With full throttle, it exceeds 40 liters. These values aren't necessarily representative, but they were lower before. The fuel consumption while idling is 1.0 l/h (according to VCDS).

I didn't log the boost pressure (target/actual), I thought the injection values were more important. However, I did check the boost pressure, and the actual value follows the target value. I checked the VTG (variable turbine geometry) using VCDS. At 1400 RPM, the boost pressure is 900 mbar in inactive mode and approximately 1000 mbar in active mode with a cold engine. With a warm engine, it's 912 mbar - 1080 mbar.

I would be very happy to find out soon why the consumption is so high, and I thank you in advance for your time and your answers.

Best regards from Switzerland.

Tobias.

Hi Tobi, which canton are you from?

LuzernPassat wrote:

Hi Tobi, which canton are you from?

Graubünden