3.0 TDI (BMK) - lots of smoke, little power

Hello,

"Exactly one week ago, I was driving my A6 for only a few kilometers when, suddenly, it lost power. Then, the emissions warning light came on, the engine went into limp mode, and the DPF warning light illuminated."

Given that the vehicle was manufactured in August 2005 and has approximately 240,000 kilometers on the odometer, the DPF (Diesel Particulate Filter) was likely faulty. This was also confirmed by VCDS, which indicated that a forced regeneration was no longer possible due to the amount of ash in the DPF.

Okay, so I replaced the DPF with a new one today. So far, everything seems to be okay. The vehicle started, and there are no more warnings regarding the filter or exhaust system. Also, there's no longer a sudden switch to limp mode when the car is stationary, which used to happen constantly with the old DPF.

Then I took it for a short test drive, and the vehicle immediately had noticeably more power. However, quite quickly, a rather black cloud started coming out from the back. When the accelerator pedal is pressed, black smoke appears repeatedly.
Okay, I initially thought he was going to remove everything from the exhaust system.
Then, suddenly, we were back in emergency mode.

The following error is consistently reproduced:

000565 - Turbocharger pressure control: Limit exceeded.
P0235 - 001 - Upper limit exceeded - Warning light ON.
Environmental conditions:
Error status: 11110001
Error priority: 0.
Error frequency: 1.
Mileage: 237,999 km
Time: 0.
Date: 2013.04.05
Time: 18:22:28

Environmental conditions:
Speed: 2982 RPM.
Torque: 362.7 Nm
Speed: 73.9 km/h
Pressure: 2284.8 mbar.
Pressure: 1326.0 mbar
Air mass/Hub: 622.8 mg/H
Temperature: 13.5°C

This error is constantly reproducible, but there's another error that I've only encountered twice so far, an error related to the LMM (Language Model Module).

000257 Air mass sensor (G70) - implausible signal.
P0101 - 002 - Lower limit exceeded.
Environmental conditions:
Speed: 1512 RPM.
Torque: 7.8 Nm.
Speed: 88.5 km/h
Key press ratio: 34.7%
Voltage: 13.98 V
Pressure: 999.6 mbar
Air mass/exposure: 716.8 mg/H.

I've already tried to find out more about the topic. I've heard about, or rather read about, VTG and AGR.

I tried adjusting the position of the variable turbine geometry (VTG) while the engine was stationary. It moves easily. Also, when the vehicle is started, it engages firmly, as it should. While I can't say for sure if it's exactly as good as if I had done it by hand, it's certainly not much shorter.
I am therefore, for the time being, not assuming any damage to the turbocharger or the variable geometry turbine.

During the last test drive, when the problem with the mass airflow sensor (MAF) reappeared, the vehicle was parked, but not immediately turned off. While idling, the engine was slightly jerky/stuttering. When lightly pressing the accelerator, it didn't really rev up; it just continued to jerk. The engine was then turned off and restarted, and the jerking/stuttering disappeared. The test drives were always to a neighboring village, which is located slightly downhill. On the way to the other village, some black smoke could be seen coming from the rear, and the performance was still relatively okay, although not as it usually is. "It wasn't until on the way back that we saw more black smoke, then the engine went into emergency mode, and then the smoke disappeared, but the power was also completely gone."

Thank you for your opinions and suggestions...

Hi Tom!

The error "Boost pressure control: Regulation limit belowsteps" in conjunction with a mass airflow sensor (MAF) error clearly indicates a leak in the charge air system.
A VTG (Vehicle Tracking and Guidance) error seems very unlikely to me, because in most cases... R. had a "rule limit exceeded" error in memory.

Okay, please check the entire piping and hose system, starting from the ATL (Automatic Transmission Line), for any oily spots, cracks, or signs of damage caused by rodents, etc.
If everything is definitely sealed there (!!), you can then take a look at the AGR.

By the way, I wouldn't wait too long to get the repair done, and I would avoid driving the car if possible, because your "new" DPF will soon become clogged again, requiring you to replace it. Also, the ATL (presumably referring to a component) will... It was constantly operated far beyond its limits, even up to the point of emergency shutdown, to the extent that it could potentially fail.

Best regards from Munich!

Hello!

However, the Mass Air Flow sensor (LMM) is located *before* the turbocharger. Therefore, wouldn't a leak in the charge air system more likely result in a reading that is *too high*? Isn't the unusual combination of error codes more likely an indication of a problem with the air intake system?

Hi,

He's not applying enough pressure. Okay, first work through what you've been given as a hint.

Hello,

First of all, thank you for your responses.

I think I understand what DieselBär30x is trying to say, at least according to my understanding. The pressure for charging is measured according to the ATL, or sometimes additionally before the ATL?
If we only consider the ATL (presumably referring to a specific document or analysis), then the explanation about the leak on the loading side makes sense to me, at least conceptually. Or am I mistaken in my reasoning?

Looking back on the recent trips, it's possible that I might have heard a slight "hissing" sound when accelerating in the car, but the engine compartment is well insulated, so I'm not entirely sure.

We're going to examine all the parts over there now. A friend is coming over...

How do you intend to measure the pressure in front of the loader when that pressure is actually generated by the loader itself?

Okay, I think I've found the bug!

The pressure hose connected to the LLK (likely referring to a specific piece of equipment) was/is leaking! You can't really see it from above, but there's a hole in it, so I can easily stick my thumb inside.

It's completely unsurprising that no boost pressure can be generated.

I've also already ordered a new or used hose. These parts are quite expensive new, costing around 220 euros.

The new "used" hose, of course, will reward you with the corresponding lifespan. These heavily stressed hoses need to be replaced to ensure a few years of trouble-free operation.
hg
Herbert.

You're right when you say that a new one would last significantly longer in terms of lifespan.

"But you also have to consider the other side; the used one cost me 45 euros including shipping, and the dealer says it has 80,000 km on it. (Of course, you have to trust that statement, but I'm going to take it with a grain of salt for now)."

The old pressure hose has seen approximately 240,000 kilometers. It's questionable whether it failed on its own, or if the unfortunately common house martens helped it along. The latter could very well be the case.

Then the vehicle will be driven approximately 15,000 to 20,000 kilometers per year.

Before I install the pressure hose when it arrives, I will, of course, carefully inspect it. If it doesn't meet my expectations, I can still return it thanks to the return policy.

Honestly, it's a bit of a calculation to figure out what to do with 220 euros versus 45 euros.

Sure, people can definitely have different opinions about it now, that's no question. Everyone has to decide for themselves.

What I don't understand is: If there's a leak in the charge air cooler system, shouldn't you be able to clearly hear it whistling at full load? Did you not hear anything?

Just driving around the city, I hear so many TDIs that are misfiring. It's enough to make my hair stand on end. Everyone needs to hear this!