Excessive soot buildup, reduced performance, and moderate gas response

Hello, as described above, I've been having issues with my Audi A4 2.0 TDI B7 since yesterday. When starting, I can press the accelerator pedal fully, and initially, nothing happens until a cloud of black smoke appears, and then the engine starts to respond. The same thing happens when I'm driving at 100 km/h in 6th gear. "Someone who wants to maintain a certain speed and then accelerate again."

There were two errors stored in the memory:
00257/000 P0101 Mass Air Flow Sensor - Implausible Signal.
00665/000 P0299 - Boost pressure control - Limit below threshold.

Both errors were intermittent and could be cleared, and the MKL (Malfunction Indicator Lamp) was not illuminated. Subsequently, I quickly borrowed and installed an LMM (Mass Air Flow Sensor) from a friend, but that didn't help either. After that, I took the car for a test drive, and I suspect the EGR valve is the culprit. Can anyone confirm this?

Here's what came out of the log:

Monday, December 1, 2014, 18:15:50:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904





"Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Es ist ein wunderschöner Tag, um spazieren zu gehen oder ein Picknick im Park zu machen. Viele Menschen genießen das gute Wetter und verbringen Zeit im Freien."
"Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Es ist ein wunderschöner Tag, um spazieren zu gehen oder ein Picknick im Park zu machen. Viele Menschen genießen das gute Wetter und verbringen Zeit im Freien."


Address 01: Engine Control Module (03G 906 016 JD)

18:15:40
3.8 mg/H Injection volume
7.1°KW Operating time (target value)
882 /min Motor speed (G28))
0.0% Accelerator Pedal Position
295.0 mg/H - Exhaust Gas Recirculation (Target Value)
285.0 mg/H Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
0.0 km/h Speed (actual value)
0.0% Accelerator Pedal Position
0.0% Position (Target) EGR Valve.
0.0% Position (Actual) AGR Valve
Monday, December 1, 2014, 18:22:56:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:22:54
1953 /min Motor speed (G28))
1020.0 mg/H - Exhaust Gas Recirculation (Target Value)
315.0 mg/H Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
2346.0 mbar - Boost pressure (target value)
1275.0 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:34:15:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:34:12
2562 /min Motor speed (G28))
330.0 mg/H - Exhaust Gas Recirculation (Target Value)
485.0 mg/H Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
1040.4 mbar - Target boost pressure.
1295.4 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:34:35:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:34:32
3171 /min Motor speed (G28))
575.0 mg/H - Exhaust Gas Recirculation (Target Value)
590.0 mg/H - Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
1050.6 mbar - Boost pressure (target value)
2060.4 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:36:05:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:36:03
3213 /min Motor speed (G28))
100.0% Accelerator Pedal Position.
1050.0 mg/H - Exhaust Gas Recirculation (Target Value)
460.0 mg/H Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
2315.4 mbar - Boost pressure (target value)
1836.0 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:36:34:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:36:32
1575 /min Motor speed (G28))
0.0% Accelerator Pedal Position
295.0 mg/H - Exhaust Gas Recirculation (Target Value)
310.0 mg/H - Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
1030.2 mbar - Boost pressure (target value)
1173.0 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 6:36:54:38025 PM.
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:36:53
2121 /min Motor speed (G28))
100.0% Accelerator Pedal Position.
1045.0 mg/H - Exhaust Gas Recirculation (Target Value)
435.0 mg/H - Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
2346.0 mbar - Boost pressure (target value)
1642.2 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:37:35:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:37:31
1491 /min Motor speed (G28))
0.0% Accelerator Pedal Position
345.0 mg/H - Exhaust Gas Recirculation (Target Value)
415.0 mg/H - Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
1030.2 mbar - Boost pressure (target value)
1071.0 mbar - Boost pressure (actual value)
Monday, December 1, 2014, 18:38:46:38025
VCDS -- A Windows-based VAG/VAS emulator.
VCDS Version: RKS 12.12.3.0
Data as of: 20140904




Address 01: Engine Control Module (03G 906 016 JD)

18:38:41
2835 /min Motor speed (G28))
0.0% Accelerator Pedal Position
385.0 mg/H - Exhaust gas recirculation (target value)
495.0 mg/H - Exhaust Gas Recirculation (Actual Value)
99.6% Exhaust Gas Recirculation (EGR) control.
1040.4 mbar - Target boost pressure.
1173.0 mbar - Boost pressure (actual value)


I would be very grateful for any helpful answers. Best regards, Frickus.

First of all, you should check if the VTG adjustment is moving, as that should only take about 5 minutes.
In the idle state, the linkage should move approximately 10mm towards the vacuum diaphragm.
The easiest way to do this is by alternately connecting and disconnecting the vacuum hose from the VTG valve.

If it doesn't engage, check if there is a vacuum present. Check if there is a vacuum, and if not, check the VTG (vacuum train control) system. Verify the VTG is functioning correctly and inspect the vacuum reservoir for leaks.

Also, also check the vacuum system for leaks.

I would only continue investigating the air supply once I'm certain that these errors can be ruled out.

A cleaning cloth or something similar may have accidentally gotten into the intake manifold (air filter) .

"Thank you for the tips, I will definitely do those first thing tomorrow. No, that's unlikely, because the problem appeared suddenly on the highway, after I had already driven 650 km on Saturday and another 200 km on Sunday." However, I still opened the air filter and checked it, just to be sure, but there was nothing clogged or blocked.
Okay, so my first step will be to check the VTG linkage and the pressure hoses. If that doesn't help, I'll remove the AGR valve and inspect it.

Autoservice wrote:

First of all, you should check if the VTG adjustment is moving, because that only takes 5 minutes.

For the sake of completeness, you can certainly do this here.
But even if the VTG (vehicle traction generator) were "dead," it shouldn't cause excessive black smoke, as long as the rest of the hardware is functioning properly.

I suspect there's a small to medium-sized leak in the intercooler system, which is causing some of the increasing boost pressure to be lost -> that's why the engine isn't pulling well at low RPMs.
Since diesel fuel is injected into the escaping air mass, it produces soot (unless the soot limit is calculated based on the boost pressure, which, as far as I know, is more of an exception than the rule).
Only when the engine reaches higher RPMs can the turbocharger pressure increase to its normal levels -> the engine starts to accelerate, but it still produces excessive soot.

I'm surprised by the high EGR target values and the full EGR activation when accelerating (I interpret the high LD target values as a pressed accelerator pedal). The AGR actual value lags behind, just like the boost pressure, then it increases, and the boost pressure stabilizes.
Shouldn't the AGR (Abgasrückführung) value be reduced and the LM (Leerlaufdrehzahl) increased during acceleration?
hg
Herbert.

Herbert wrote:

Shouldn't the EGR value be reduced during acceleration, and the LM (lambda) increased?

The physical EGR target is the air mass
For the EDC15 system, the N75-TV value is generally low at full throttle, but this doesn't necessarily have to be the case for other EDC systems.

Do you mean that what is listed in the log as "AGR Desired/Actual" actually represents the air mass?
hg
Herbert.

Herbert wrote:

You mean that what is listed in the log as "AGR Desired/Actual" is actually the air mass?

Yes.
While I can only see the log as a collection of numbers again, for example, in the post by TS:

18:22:54
2346.0 mbar boost pressure (target value).
1020.0 mg/H Exhaust Gas Recirculation (Target Value)

It only makes sense together if the target AGR value is represented as a luminance value.

The log can be read. If not using a dedicated tool like Scope, you can import the data into Excel as a .txt file and then specify the delimiters.
If LM and LD are significantly lagging behind the target and then suddenly increase, it suggests an issue with the LD regulation, which could indicate problems with the VTG (Variable Transmission Gear).
hg
Herbert.

Herbert wrote:

If LM and LD are initially significantly below the target and then increase, it suggests the LD regulation is at play, which could indicate VTG issues.

1. The LuMa-Soll value at WOT (Wide Open Throttle) is usually not a realistically achievable value without full LD (Load Dump).
2. If the problem were only related to the VTG hardware, the vehicle shouldn't produce excessive smoke – unless it has been poorly modified.

I've started working on the intercooler system, and when oil started leaking out of the hose between the intercooler and the throttle body, I thought I'd remove the throttle body and take a look at what's causing the problem.
"Everything was completely carbonized, so the EGR valve and intake manifold were also removed at the same time." It doesn't look perfect, but it's very authentic.

Hello,

Replace the AGR valve with a replacement part from the aftermarket.

The turbocharger pressure regulation is faulty. Engine control unit: stock or tuned?
Mileage? With over 200,000 km on your car, and if it's your own vehicle, you can order a new throttle body (a readily available replacement part) at the same time.

Best regards, Rainer.

Hi Rainer, the engine control unit is original. It now has 195,000 km on it and it's my own car. After a thorough cleaning of the throttle body, EGR valve, and intake manifold with turpentine, I've found the problem: the EGR valve is the culprit. The valve has failed and is no longer working or sealing properly. I've managed to verschandeln the rest of the components. But still, thank you in advance to everyone for your thoughts and suggestions. I will let you know if it was indeed the error.

...one more thing: How on earth can a BRE motor produce soot? Here, a closed DPF is installed as standard.

There are then two possibilities:
- defective (broken, etc.), with the possibility that parts could block the exhaust.
- removed, which would not only be pointless but also prohibited.

"So, he's definitely not removed, because it's still inside. According to the previous owner, the DPF was already replaced, and Audi confirmed this, as it was done there. Is it broken? It might be, but my guess is that the broken throttle valve in the EGR system allowed too much exhaust gas to enter the combustion chamber, and the DPF was simply "overwhelmed"." If the new EGR valve arrives tomorrow or on Friday, I will report back whether the excessive soot has stopped. If not, the troubleshooting process will continue.

This type of DPF cannot be "overloaded." If too much soot accumulates, it will become clogged and fail. Then it's finished.