TDI AHF: Engine Problems & Solutions

Hello,
I hope I'm not doing anything wrong by describing my unresolved issue again here, especially since I've already gone through the general support channels and haven't found a solution yet. If this is inappropriate, please simply delete the post and apologize; it was due to lack of knowledge.
The chronology:
VAG TDI AHF engine with 110 horsepower.
04.2005: 125,000 km - running on BIODIESEL; leaky pump and occasional power drops.
04.2005: Pump repair at a BOSCH service center.
06/2005: Still experiencing intermittent performance issues; the error log indicates "unreliable signal from mass airflow sensor, sporadic error." This is completely sporadic and unexpectedly occurring.
The LMM (likely referring to a language model) has already been changed twice in the past, but there has been no improvement.
09/2006: New battery installed (NBF), supplied by Mercedes, but no improvement.
Supercharger pressure control valve replaced - no improvement.
Tachogenerator disconnected for a test over a distance of 200 km - no improvement.
10.2006: EGR valve blocked for approximately 1,000 km to test with additives - no improvement.
11.2006: Out of desperation, the Mass Air Flow (MAF) sensor was replaced again by BOSCH - no improvement. BOSCH measured the boost pressure randomly when the error occurred: 0.5 bar below the target value.
Finally, Bosch's statement: something in the exhaust system is intermittently blocking the exhaust flow, which is causing the power interruptions.
"I then switched to 0W40 synthetic oil at 165,000 km and replaced the diesel filter - and lo and behold, the error didn't reappear for about 3,000 km, but then it started appearing again with increasing frequency. First every 800 to 1,000 km, then every 600, 400, 200, and so on. I inspected the fuel tank for oil sludge or anything similar - it was absolutely clean. I changed the diesel filter anyway every 30,000 km, and most recently every 15,000 km."
I'm as clueless as the BOSCH engineers that the BOSCH service contacted.
My gut feeling tells me that there's only a small issue causing this problem, but no workshop has been able to fix it so far. Does anyone have any ideas?

Can you please define "outages" in more detail?
Sudden loss of power? Sudden decrease in power?
Or gradually?
What do the lights in the instrument cluster do?

Have you seen the new Relais 109 yet? The symptoms are similar to what I experienced when my relay was slowly failing.

Was ist die Wahrscheinlichkeit, dass der Fehlercode "Turbocharger pressure limit exceeded" im Fehlerspeicher angezeigt wird?

hello Tagessuppe,
First of all, thank you for your reply.
The power suddenly cuts out, as if the turbo shuts off (leaving approximately 40 to 50 horsepower). The error memory consistently showed something like "Mass airflow sensor: implausible signal, intermittent error."
I don't have a new relay 109.
Best regards,
Bernd.

If a relay is defective, it's more likely that the entire control unit will fail. A typical symptom would be the vehicle not starting after being driven.

However, I would still replace the relay, as it's relatively inexpensive and easy to do.

How about logging for a long enough period of time to catch one of those glitches in the log?

I can repeatedly cite the example of the Ibiza ASV, which suddenly experienced brutal and abrupt performance drops after the automatic update.

Laptop connected, colleague driving and causing the misfires... you could immediately see that the lambda sensor was dropping to zero.
It was a loose connection in the cable or plug.

Without the LOG while DRIVING, we would never have found it.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Then it really doesn't sound like relay 109, because in that case, it wouldn't be getting any power, and the lights in the instrument cluster would start acting up.

Could the problem really be caused by a break in the wiring between the mass airflow sensor (MAF) and the engine control unit (ECU)?
If you forget to plug the cables back in (like I did).
Then perhaps only 50% of the performance will remain. That's much less than with a "faulty" mass airflow sensor (MAF).

Examining the cables more closely would probably be the best approach.

Thank you, Uwe. Thank you, Tagessuppe.
The performance is roughly equivalent to what remains when I disconnect the MAF sensor or pull off a vacuum hose from the boost pressure control valve. 50 horsepower might be about right, which is definitely worse than my wife's diesel Kangoo with 63 horsepower!
I'm going to check the cable all the way to the control unit (I wonder exactly where that is located?), especially since our rodent has already chewed on the coolant hose of the Kangoo before.
Best regards,
Bernd.

Of course, thank you also to dieselmartin.
"Regarding the logging issue while driving, I will definitely discuss it with VAG by the end of the month. If I haven't found a solution myself by then, this will be my last attempt to get help from a workshop."
Regards,
Bernd.

Forget about getting a log rack from Volkswagen.

They all just have those error code eliminators that are screwed into the wall.

Laptop, VAGCOM, DIY!

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

To be fair, I have to say that my dealer already does this and also has employees who are capable of analyzing the data. The only problem is the cost involved.
You can almost buy the software and a diagnostic tool for that price.

It could also be a faulty cable or connector to the mass airflow sensor (MAF). The error code related to the MAF should then be stored in the engine control unit (ECU). Try spraying your MAF connector with contact cleaner.
If you are using a part from Mercedes (Pierburg), it uses different contact material which can cause occasional connection problems with the original connector of the SGAF system.

Best regards,
Christian.

Hello,
I took out my camera and tried to get some pictures. I'm starting to doubt everything. Can someone tell me if the fuel tank cap is installed correctly? The larger arrow points towards the rear of the car, while the smaller arrow probably indicates the direction of flow towards the engine. Could the hoses be reversed? Anything is possible, as I said, I'm doubting everything I've put together on this car so far; sometimes you can end up "fixing" something by breaking it further.
What is the expert opinion on the Russ turbocharger?
1. normal
2. Reference to damage or harm.
3. Tolerable because it may be caused by a sudden drop in boost pressure?
Who has experience with this?
Thank you in advance to everyone.

Hello Bernd,

If I interpret the photo of the loader correctly, I would say there is a leak .

Soot at this location is definitely not normal -

I recently replaced my charger - it's a VTG unit - and I couldn't find any soot on the exterior of the casing.

Best regards,

Wolfgang.



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Yes. It appears there's a leak coming from the VTG adjustment mechanism.

Could it be that the VTG (Variable Transmission Gear) gets stuck in the "open" position?
After that, the car would likely enter a limp mode because there would be little or no boost pressure, or it would build up too late.
My EGR valve went into limp mode due to a leak in the charge air system and the resulting lack of boost pressure, but without the glow plug indicator light illuminating.
However, there should then be an error message displayed.

No, I don't think it's likely related to the leak in the VTG adjustment system.

What do you think?

The power suddenly disappears, as if the turbo shuts off (approximately 40 to 50 horsepower remain at that point). The error memory always showed something like 'MAF sensor: implausible signal, intermittent error'.

What does the expert community say about the Russ with a turbocharger?

Could it be that the VTG gets stuck in the 'open' position?
After that, the car would likely go into emergency mode because there would be little or no boost pressure, or it would build up too late.

Hello everyone,

At first glance, it seems like a turbo problem.
I don't believe there would be a fault code entry for the AHF (assuming 'AHF' refers to a specific system or component), because the software doesn't define a threshold for when the actual value falls below the target value.
(@Rudi or Rainer... was it you who had the heart failure, or someone else?)

The only thing that can be identified as unsuitable is the lack of air mass, which cannot be generated if there is no LD (likely referring to a specific technology or component).
Therefore, the LMM error fits into the picture.

Laptop, VAGCOM, DIY!

I can only wholeheartedly agree.
During a log ride, you can see the desired and actual values of the load cell (LD) and the control signal for the variable geometry turbine (VTG). If something is not right, it's immediately apparent. Also, the fuel injection amounts will then no longer be correct.

Best regards, Jochen.