Performance deficiency / Smoking restrictions, ventilation system

Hello.

I'm having a small problem with my Passat 3BG Variant.
The engine is an AVF series with approximately 230,000 kilometers and a TT5 EYF transmission. (The timing belt was replaced at 176,000 kilometers).

I'm experiencing an inexplicable lack of performance; it feels like I'm driving around with the handbrake on. (Which is now released ).
I then logged a test drive (MWB 8, 10, 11) and discovered that the soot limit constantly restricts the fuel injection.
That's probably the reason for the feeling of having pulled up the handbrake.

When the air mass rises, the soot limit also increases, which, based on my extensive reading of technical articles, suggests a lack of airflow.
But I'm not entirely sure about that.

I already replaced the mass airflow sensor because the old one was showing a lower air intake reading (a maximum of 600 mg/H).

Yesterday, I also checked the basic settings for the VTG (Variable Turbine Geometry) and AGR (Abgasrückführung) systems (in the engine control unit).
The engine's RPM increased to 1400, and the boost pressure fluctuated from 990 millibars to 1170 millibars while the VTG (variable turbine geometry) adjusted its position.
The boost pressure actually follows the target value on the curve, but I'm not entirely sure if that's correct or if it's regulating quickly enough.
The vertical travel guide rod moved up and down quite quickly and reached its end position without any noticeable jolting. (It's hard to see, but after raising and lowering it about 10 times, I was sure of it.)

This morning I opened the air filter housing and found quite a few insects inside the air filter. It was replaced during the last inspection, about 24,000 km ago.
I immediately exchanged it and put everything back together.

Attached are three logs, one from April, which looks quite messy because I didn't yet know how to properly create a log file.
The other two show the power loss before and after the filter change.

However, the data from the log in April shows that the boost pressure builds up better and reaches the target value very quickly.
Should I perhaps remove the turbocharger and verschandeln the variable geometry turbine (VTG)?

Here's everything I've done to the engine since April:
- EGR cleaned.
- Intake manifold removed.
- Vacuum hoses for EGR and turbocharger replaced.
- LMM replaced.
- Air filter replaced.

The inspection is coming up soon (in 2000 km). The diesel filter should also be replaced then. However, the missing mass airflow sensor shouldn't be related to that.

Do you have any other ideas or suggestions that could help me regain my previous level of performance?
Do you agree with me that I seem to be having a problem with my air mass?

Thank you for your suggestions and feedback!

Hello.

I would like to re-enter my serial number, but I am unable to do so.
All I see is the following:

You can ask questions using your support key (e.g., the German VCDS serial number).
You can find the VCDS serial number on the "About..." screen within the VCDS software. For GS-911 or Bavarian Technic, the serial number needs to be entered on the diagnostic cable itself.
You can purchase a corresponding diagnostic system with a support key or just the support key here.

But there's no way to enter the number.
Und eine PN konnte ich leider auch nicht zurückschreiben... Sorry!

EDIT:
I've updated the number; it should work now!

Hello,

Quote:

I've updated the number; it should work now!

ok, thank you.

Since the target pressure is being reached in your table, but the air mass is slightly too low, there are two possible causes:
- Air mass flow is too low in reality due to a bottleneck, e.g., a faulty silencer on the exhaust, a tilted catalytic converter ceramic core, a defective or stuck EGR valve, a piece of cloth sucked into the intercooler, etc.
- Mass airflow sensor defective.

If you experience excessive exhaust smoke (visible as a slight dark plume in the rearview mirror) at around 4000 rpm, with the boost pressure set and under full throttle, then there is likely an issue with the mass airflow sensor.

If the exhaust looks clean, it's likely that the air mass measurement is simply too low, but is actually okay. -> Is the correct air mass sensor installed? Are +5V reaching the power supply of the air mass sensor? Are the cables/connectors to the air mass sensor corroded?

When it comes to air mass sensors, it's best to use original parts. The measuring sensor itself (which is inserted into the housing with just two Torx screws) likely costs around 80 euros.

See also:
/viewtopic.php?t=3347&highlight=mass airflow sensor

Best regards, Rainer.

Okay, that sounds like it's going as expected so far.

How can I check if the exhaust system has any leaks?
Because, unfortunately, a magnifying glass or something similar is not available.
So, does that mean taking it apart and looking inside? Or can you tell by tapping on the outside if something is rattling around inside?

It is very unlikely that a cloth was sucked in.
I'm not ruling it out just yet.


The AGR (Abgasrückführung) definitely seems to be defective or deactivated.
During the initial positioning phase of the AGR (Adaptive Gas Release), the air mass does not change at all.


I'll pay attention to the smoke again on my way back today.
I'm going to take another measurement right away. I reprinted the technical article.
I had already read it.

Thanks for now, I'll report my measurement results tonight!
Best regards,
Florian

dieselschrauber wrote:

... can be caused by two things: - Air mass flow is too low in reality due to a bottleneck, e.g., a faulty silencer on the exhaust, a tilted catalytic converter ceramic core, a defective or stuck EGR valve, a piece of cloth sucked into the intercooler, etc. - Mass airflow sensor defective.

I would actually rule out a piece of cloth in the intake manifold, because then the restriction would be located before the lambda sensor. However, an imbalance in the mass airflow-lambda relationship can only arise systemically, in my opinion, if the restriction is located behind the lambda sensor.
Another possible cause: Carbon buildup from the EGR system in the intake manifold (including the valves!), which was not removed during the EGR cleaning mentioned in the post.

Gilliearnie wrote:

How can I check if the exhaust system has any leaks? Best regards, Florian

.

Carefully loosen the flange connecting the turbocharger to the exhaust pipe and check how much pressure is escaping.

RedR32 wrote:

Carefully loosen the flange from the turbocharger to the exhaust manifold pipe, and check how much it blows out.

It probably won't achieve much if you don't have a sense of what is considered normal, just like me.
Tapping the exhaust pipe can quickly reveal whether the catalytic converter has dissolved or is in the process of dissolving.

RedR32 wrote:

Gilliearnie wrote: How can I check if the exhaust system has any leaks? Best regards, Florian . Possibly loosen the flange from the turbo to the exhaust pipe carefully, and check how strongly it's blowing out.

I agree with Matthias.
This method is only practically applicable in a stationary setting, but even with full throttle bursts, only fractions of the exhaust flow rate achieved during actual driving at full throttle are reached. Therefore, a bottleneck in the exhaust system that significantly affects maximum power (Pmax) does not necessarily have to be clearly evident during stationary tests.

I would rather compare the behavior of the LD (load detection) system in the MWB11 with vehicles that have intact motor functions, because if there are restrictions on the exhaust side, the VTG (variable geometry turbine) needs to be closed further to achieve the desired LD value.
Unfortunately, this testing capability is compromised by various potential sources of error, such as misaligned VTG vanes, minor defects in the engine's pneumatic components (which do not lead to a complete system failure), and ultimately, the already reduced exhaust flow, as seen here because the engine is running under suboptimal conditions.
Based on my initial assessment, a 60% TV-Log value at Pmax doesn't necessarily indicate a clear problem originating from the exhaust side. Therefore, I would first thoroughly inspect the entire area between the LD sensor and the combustion chambers for any potential restrictions or bottlenecks.

ulf wrote:

dieselschrauber wrote: ... there are two things that could be the cause: - Air mass flow is too low in reality due to a bottleneck, e.g., a defective muffler on the exhaust system, a tilted catalytic converter ceramic core, a faulty or stuck EGR valve, a piece of cloth sucked into the intercooler, etc. - Mass airflow sensor defective. I would actually rule out a piece of cloth in the intake manifold, because then the restriction would be located before the lambda sensor. However, an imbalance in the mass airflow/lambda relationship can only arise systemically, in my opinion, if the restriction is located behind the lambda sensor. Another possible cause: Carbon buildup from the EGR system in the intake manifold (including the valves!), which was not removed during the EGR cleaning mentioned in the post.

Is that ?

Okay.
So, I checked the voltages earlier. (Engine off, ignition on), and I had readings between 2 and 3 volts, and between 4 and 2 volts.

I'll check the printer hoses tonight or tomorrow night.
Sure, I'll translate the text and then perform the tapping test.

**Translation:**

"Please provide the text you would like me to translate from German to English."

Best regards, Florian.

Here's the translation:

"Or maybe a quick trip with a loose flange, using MWB logging. Just tapping doesn't tell the whole story; you won't notice broken catalytic converter pieces that are stuck in the pipe."

RedR32 wrote:

Or a quick trip with a loosened flange, using MWB logging. Just tapping doesn't tell the whole story; you won't notice broken catalytic converter pieces that are stuck before the pipe.

Okay, this is how you could hide bottlenecks in the AgA (agricultural pipeline).

What I also noticed in Log 4: The motor never comes out of the "haze" or "blur."
However, I believe that the usual bottlenecks in the gas passages only become increasingly significant towards the maximum power output (Pmax), meaning that the engine, for example, doesn't start to exhibit signs of reduced performance until around 3000 rpm.

Here, the LuMa/LD trend seems to be completely shifted downwards compared to normal logs – as if someone had, for example, connected a diode in the LMM signal line to reduce the EGR rate .

Hi there,
Does the EGR valve actually close completely?

Quote:

I would like to check that mechanically.

The EGR definitely seems to be defective/deactivated.
During the initial positioning movement of the AGR, the air mass does not change at all.}
That doesn't prove anything; it merely redirects suspicion in the same direction. If the EGR valve is open, not enough fresh air will be drawn in despite the turbocharger pressure, and the engine will remain in the soot reduction mode.
hg
Herbert.

Good morning.

Okay, I disconnected the boost hose and the vacuum hose yesterday.
There were no bottlenecks to be found, only oil stains on the walls.

The AGR valve was also clogged, so I cleaned it with brake cleaner.
I also removed the intake manifold; it was a pain to work on, but I cleaned it.
Die sah recht gut aus, 1- 2mm Ruß direkt am Eingang, mehr nicht. Als es sich aufteilte sah man (Mit Spiegel) das Metall durchschimmern. So it was just oil.
I also checked the valves, and there was nothing but oil inside.

The EGR valve is completely blocked, and there was a greenish, greasy sludge stuck under the valve seat (on the exhaust side). I have no idea where that could have come from...
The AGR is still moving.
Could it be that the vacuum valve is faulty and constantly being activated?

Okay, now about the turbocharger: I didn't remove it completely, but I did turn the turbine.
An einer stelle geht es etwas schwergängig... Turbo bald im Arsch? Damage from improper storage?
Okay, in my opinion, it spins up to 120,000 rpm, right? And shouldn't you give it a little nudge, and then it should spin for about 2 or 3 revolutions on its own?
But with that thing... it always got stuck on one side, so it was a bit awkward.
Damn it, dwt.

I'll disconnect the exhaust pipe sometime tomorrow or Monday, depending on when I have time, and then log the data again.

Now, it's my youngest child's birthday .

Best regards and have a great weekend! Florian.

Quote:

An einer stelle geht es etwas schwergängig... Turbo bald im Arsch? Damage from improper storage? So, IMHO, it spins up to 120,000 rpm, right? And then you should give it a little nudge, and it should actually spin for 2-3 revolutions on its own, right?

That's bad and not normal. The loader shaft needs to rotate easily and without any resistance.

Theoretically, it is conceivable that due to increased friction, the VTG (variable turbine geometry) might need to be adjusted further to achieve the desired pressure, which would result in a lower air mass flow rate. However, in practice, this "increased friction" is unlikely to be significant because the frictional heat generated would long ago have completely destroyed the bearing system.

I can imagine that the difficulty in rotating the loader shaft was caused by carbon deposits resulting from overheating, which may have been due to a blocked exhaust system.

Have you checked the catalytic converter and muffler? Have you already done a test drive with the exhaust pipe loosely attached to the turbocharger with just 3mm of clearance?

Best regards, Rainer.

Gilliearnie wrote:

The EGR is completely blocked, and there was greenish, greasy sludge stuck under the valve seat (on the exhaust side). I have no idea where that could come from...

How is it blocked? With a solid plug without a hole?

Quote:

The EGR is still moving. Could it perhaps be that the vacuum valve is defective and constantly being activated?

If you mean the silver plate, the valve is normally closed by a spring and opened by pulsed vacuum pressure.
If you're referring to the solenoid valve, it could theoretically get stuck in the open position, but as far as I know, this is very rare or has never happened.

Quote:

Now, regarding the turbo, I didn't remove it, but I did turn the turbine. An einer stelle geht es etwas schwergängig... Turbo bald im Arsch? Damage from improper storage? Okay, in my opinion, it spins up to 120,000 rpm, right? And shouldn't you give it a little nudge, and then it should spin for about 2 or 3 revolutions on its own? But with that thing... it always got stuck on one side, so it was a bit jerky...

You probably think of ball bearings when you consider the expected lag. However, the GT1749 turbochargers have plain bearings, and in those, the engine oil immediately dampens any initial momentum. The feeling is roughly like a spoon handle in clear honey. At low, hand-cranked speeds, the shaft might rotate a maximum of 1 revolution.When the shaft is tilted, it becomes increasingly difficult to turn. However, a noticeable increase in resistance when turning the shaft, always occurring in the same position, is not normal, as Rainer pointed out.