Luftmasse zu hoch A6 4F 3.0 TDI ASB | Posts 24+

Hi,

I just found the injection start time in the log, and it also looks okay. The back pressure on the DPF seems to be within the acceptable range. I'm starting to run out of ideas.

Slipping brake, car rolls easily?

Best regards, Rainer

dieselschrauber wrote:

Hi, I just found the injection start time in the log, and it also looks okay. The back pressure on the DPF seems to be within the acceptable range. I'm starting to run out of ideas. Slipping brake, car rolls easily? Best regards, Rainer

Welcome to the club

Yes, the car is rolling far, far away. Wheels are cold.

Does the engine perhaps try to regenerate indefinitely? Does the mileage since the regeneration show, and is it in DPF regeneration mode?

The exhaust temperatures in your log are too low (normal), perhaps the system hasn't been regenerating properly during logging...

Best regards, Rainer

dieselschrauber wrote:

Is the engine possibly trying to regenerate indefinitely? Does the mileage since the regeneration show, and is it in DPF regeneration mode? The exhaust temperatures in your log are too low (normal), perhaps the system hasn't been regenerating properly during logging... Best regards, Rainer

Hello Rainer,

I've been closely monitoring the DPF since the cleaning in the summer. It regenerates very rarely. At the time of the last log, it had been 800km since the last entry, and there had been no attempts or failures.

Regarding the exhaust temperatures... I also found them to be very low while driving, but during the last forced regeneration (a few weeks ago as part of the troubleshooting), the temperatures before the cat/before the DPF reached 684.4°C/631.3°C. I believe this is plausible. Furthermore, I observe a meaningful and graded temperature difference between ATL, DOC, and DPF, even though the actual levels are relatively low in everyday use.

I'm going to leave it like this for a couple of weeks. I'll be away on business until the 20th. After that, I will review the entire text more carefully.

Thank you for your consideration and best regards.

Bo

Possibly, the AGR valve is malfunctioning intermittently, or the corresponding solenoid valve? The RPM range with high fuel consumption would fit, as it's where the engine works the hardest...

Is the ventilation of the underpressure system free?

Best regards, Rainer

I think I've got it. I looked at a whole bag of logs from the past few weeks over the weekend. I've also noticed that, except for very long stretches on the highway, I've never had a transmission oil temperature above 60°C.

Subsequently, I checked a log where I could see the transmission status. And indeed, when driving on a 100km federal highway, I reached a maximum of 51°C, and the TT (Transmission Temperature) did not exit the warming mode. A mistake will not be dismissed.

Does anyone know if it's possible to access the sensor without having to open the gearbox? Or is it embedded in the mechatronic module? I will be able to see it after the next weekend.

Greetings

Bo

Ste.Bo wrote:

Does anyone know if it's possible to access the sensor without having to open the gearbox? Or is it embedded in the mechatronic module? I will be able to see it after the next weekend. Greetings Bo

The temperature sensor is firmly mounted on the control unit board.
The transmission control unit for the 6HP19A is located inside the transmission.
It is a permanently encapsulated PCB that is mounted above the mechatronic components and attached to them. It is therefore always immersed in the oil bath of the oil pan. Simply removing it is not possible, or Replace, as the WFS is VIN-bound.
Unfortunately, this means that the G93 bulb cannot be replaced individually, and it is also not available for individual purchase.

Since the automatic transmission's temperature control in the A6 4F is regulated by the engine's coolant control via the coolant, I would recommend checking the engine temperature. The ATF oil cooler is integrated into the water cooler on the driver's side. My automatic transmission also behaves differently since a new thermostat was installed. Consumption has also decreased.

Greetings, Mpire

Mpire wrote:

The temperature sensor is firmly mounted on the control unit board. The transmission control unit for the 6HP19A is located inside the transmission. It is a fixed-mounted PCB that is mounted above the mechatronic components and is always immersed in the oil bath of the oil pan. It cannot be simply removed or replaced, as the WFS (Webasto Fuel System) is VIN-specific. Unfortunately, this means that the G93 bulb cannot be replaced individually, and it is also not available for individual purchase. Since the automatic transmission's temperature control in the A6 4F is regulated by the engine's coolant control via the coolant, I would recommend checking the engine temperature. The ATF oil cooler is integrated into the water cooler on the driver's side. My automatic transmission also behaves differently since a new thermostat was installed. Consumption has also decreased. Greetings, Mpire

Hello Mpire,

Thank you for the information. I exchanged the thermostat with the one from the BPP. It didn't make any difference. However, since the one I had was also around 180,000 km, I will probably try with a new one. Although I hesitated because the opening at 87°C was visible in the temperature profile.

Greetings

Bo

Are you both absolutely sure that there are no other thermostats in the small cooling water loop of the gearbox? "This was at least the case with the Passat 3C and DSG, and it seems quite plausible to me..."

guste100 wrote:

Are you both absolutely sure that there are no other thermostats in the small cooling water loop of the gearbox? "This was at least the case with the Passat 3C with DSG, and it seems quite plausible to me..."

Yes, I am 100% sure. The 09L gearbox only has an external water-oil heat exchanger for the gearbox in the Audi A8 and Q7.
It shares the water cycle with the motor and an external thermostat.

In all other models, it is as described in the previous post, the gearbox oil cooler is integrated into the water cooler.

Greetings, Mpire

guste100 wrote:

Are you both absolutely sure that there are no other thermostats in the small cooling water loop of the gearbox? "This was at least the case with the Passat 3C with DSG, and it seems quite plausible to me..."

Yes, Mpire is definitely right! The A8 and the Tuareg, both with the same engine, have different oil coolers and a small inline thermostat. Not an All-Road!

Greetings

Bo

Okay. Last weekend, I was finally able to dedicate myself to my beloved "Dicken". Here are the latest updates.

The thermostat is new. However, I am unable to achieve above 90°C on the main road. The temperature reaches approximately 87°C after about 6-8 minutes, and then oscillates around this opening temperature of the thermostat with +/-2°C. Don't forget, the temperature sensor has already been replaced.

Since then, I've driven approximately 1200 km.

The ATF temperature does not exceed 60°C without the highway. The slip during acceleration is enormous. VCDS also shows a permanent "warm-up mode" after 100km on the highway, and the oil temperature is between 52-56°C (which is impossible since the radiator is heated to 87°C). I checked the gear oil level and refilled approximately 0.4 liters. No improvement.

A faulty oil temperature sensor in the TT would explain the enormously increased fuel consumption in the city and during dynamic driving at that time. I still don't know what I'm going to do with it...

Regarding the still significantly increased fuel consumption at low loads on highways/long distances (Tempomat 80 to 140 km/h, even when I have warmed up the gearbox on the motorway), I am unable to proceed further.
I have observed a final, unexplained anomaly in the logs (also shown above). The boost pressure sometimes deviates from the set value by 50-120 mbar, but not always. Transient, he always fits, and the deviation can be found in all % VTG control systems, provided the system is stationary. Therefore, I am excluding the VTG.

The AGR valve has been cleaned again, and new seals have been installed. The intake duct and individual LLK (air intake ducts) were checked on the weekend. Everything is now sealed. Where can I find the missing mbar? Someone suggested that it could be oil condensate on the fresh air scoops from the turbocharger. Cleaning should help. Does anyone have any experience with that?

Greetings

Bo

Ste.Bo wrote:

...Someone suggested that the oil condensate might be coming from the fresh air scoops of the turbocharger. Cleaning it out is supposed to help. Does anyone have any experience with that? Best regards, Bo

But I think that's just a rumor!
Now, think about who's really doing the work! If there is a valuable oil film, then definitely not for long!
haithamina

haithamina wrote:

....Someone finally suggested that the oil condensate might be on the fresh air scoops of the turbocharger. Cleaning it out is supposed to help. Ste.Bo wrote: Does anyone have any experience with that? Best regards, Bo But I think that's just a rumor! Now, think about who's really doing the work! If there is a valuable oil film, then definitely not for long! haithamina

Hello,

I spoke with the relevant colleague about his comment. He directed me to the following document.

"Investigations into the cause and effects of contamination in the turbocharger radial compressor" by Christiane Duwe, Master thesis in the field of aerospace engineering and at DAIMLER AG.

Now I understand. Minor imperfections and discoloration that are barely visible can cost trucks over 20% of the relative pressure, while cars cost 10-15%. Causes include blow-by and KGE (Kritische Geschwindigkeitsgrenze) under unfavorable load profiles.

Greetings

Bo

A very happy new year to you!

My problem is gone. As often happens, it turned out to be a coincidence that the problems coincided with my AGR change. The increased fuel consumption was not due to the higher AGR rate.

Thanks to your comments, I was able to find and fix many minor issues (including a few unnecessary ), but in the end, my main problem was actually the Tiptronic.

Now at 223 TKM, I have decided to perform a major service, including washing (TEM) and re-oiling, as well as a software update. This also addressed the issue with the internal GO temperature sensor.

Alles klar. Aber jetzt haben meine Frau und ich unsere Autos getauscht. Wir haben jetzt einen 2.0 TDI rund um unser Haus und ich fahre wieder Strecken mit dem V6. I am now 2200km since the last regeneration, and the car is running with an average of about 8 liters instead of >10.5.

Thank you again to everyone.

Greetings

Bo

Thank you for your feedback

Wishing you a happy new year too!