VTG Closure Fixes Temporary AVB Light Issues

I have a Passat that sometimes loses power in second gear.
I logged MWB 8, 10, and 23.
The mass airflow sensor (MAF) value is too low; if it's not working correctly, you can also see this in the engine control module (ECM) data, specifically in memory location MWB8/4. However, if I briefly release and then reapply the throttle, it works normally. I also hear a clicking sound from the EGR valve when idling. I mechanically blocked the EGR valve and thought that was the problem solved. But it's not. I can only trigger this issue in second gear. Once I release the gas and then apply it again, it works normally. Also, the MAF value is then correct.
Is it really just the mass airflow sensor (MAF) that's causing the problem? Unfortunately, I don't have one to test with. I can't quite picture how that would be, since it only happens in second gear.
Has anyone else experienced this problem?

Hello,

Quote:

I also hear a clicking sound from the EGR valve when the engine is idling.

Is the vacuum system sealed? In a vehicle with an EU III emissions standard, it may not be possible to simply disable the EGR valve. Is the EGR monitored in this case? What error codes are stored in the diagnostic memory?

Best regards, Rainer.

"No, it is not yet being monitored, and there are no error codes stored."
I placed a metal sheet next to the pipe.

Today I tested the mass airflow sensor (MAF) from my Golf, and it's the same – no improvement in performance.
The hose was disconnected from the bypass valve to rule out a faulty valve, but it didn't solve the problem.

I temporarily raised the smoke sensor for testing purposes, and after that, I was able to trigger the error once, but not again. However, the power also seems to come on very late.

The turbo and the N75 valve have already been replaced by someone else.

Could it be due to sticking valves, or does this engine also have a camshaft with oil plugs?
I'm only familiar with worn camshafts through the sound of a noisy intake.

That's quite an interesting situation: the boost pressure is increasing, while at the same time, the air mass is decreasing!
Please generate a log similar to the previous one, but this time only including data from MWB 10 and 11.
"Please try flooring the accelerator pedal from around 1200 RPM and holding it down as long as possible in the highest gear."

My currently favored idea is that the VTG (variable turbine geometry) is closing too much, and therefore producing a gas buildup all the way into the intake manifold .

Yes, MWB 11 should be it.

As the engine speed and boost pressure increase, the air mass can sometimes drop to a level below idle. If the EGR valve is closed, this shouldn't be possible.

I can't imagine how it's possible to achieve even more acceleration with a "real" value of approximately 415 mg/H at 3500 RPM, especially considering what the log indicates is happening.

How old is the LMM?

Here's the log.

I was also able to trigger it in the third gear.
It starts to knock around 3200 RPM, but that's because I injected too much fuel since I increased the smoking map. I'll revert it when it's working properly.

In 4th gear, everything went back to normal; the gas was gone and then reappeared.

I've already tried the car wash at LMM (it works), but it didn't make any difference.
He accelerates faster because I increased the fuel enrichment curve.

Quote:

In the 4th gear, everything was back to normal, as the gas pedal went down and then up again. I've already tried the car wash at LMM (

), and it works, but it didn't change anything.

Sorry, I overlooked the LMM

Quote:

. Let's summarize: Fehler tritt meist nur im 1+ 2. Door open. The air mass is too low, resulting in a delayed build-up of boost pressure. From 3rd or 4th gear upwards, the mass airflow (MAF) values are okay – the boost pressure builds up as specified. What happens if you accelerate in the first and second gears, but increase the engine speed at a slower rate over time (similar to how it increases from the third gear onwards)? It would be interesting to see if the LM values then increase steadily, or whether they still experience drops. Hypothesis: Possible temporary blockage of the airways when the engine speed increases rapidly. For example, a catalytic converter, muffler, or something in the intake system.

Could it be due to stuck camshafts, or does this engine also have the rocker arm shaft with oil plugs? }

Hmm, shouldn't the error always occur?

I've experienced it in third gear as well.
Air mass too low, delayed LD build-up – that is correct.

Das mit langsam steigender Drehzahl muß ich erst probieren, Fahrzeug gehört einer Frau, glaube nicht das die die "Heizerin" ist. PI'm definitely going to rob him.

You're right, if it were the camshafts, it would always be happening.

I need to follow up and ask again whether this issue occurred immediately after the turbocharger replacement or later on.

When accelerating slowly, the same thing happens: the mass airflow (MAF) values also decrease.

chli1976 wrote:

Here is the log. I was also able to trigger it in the third gear. It starts to knock around 3200 RPM, but that's because I injected too much fuel since I increased the smoking map. I'll revert it when it's working properly. In 4th gear, everything went back to normal; the gas was gone and then reappeared. I already tried the self-service machine at LMM (it works), but it didn't change anything. He accelerates because I increased the smoking characteristic curve

. Could you please upload that as a proper .xls file (with data in each column)?
I don't have time to process that using the "text to columns" function ten times.

Hi Ulf, I have Excel 2003 and can open it normally, of course using the CSV converter beforehand. Which version doesn't require the converter?

I took two screenshots for you.

chli1976 wrote:

I took two screenshots for you

. They are not very helpful to me, because I usually create charts to look at; that is much more understandable for me than just rows of numbers.

Hello.
Okay, so the learning rate (LD) is building up much too slowly, and of course, the learning momentum (LM) is also far too low. Please compare it to this log: /viewtopic.php?t=13262&highlight=
If the mass airflow sensor is working correctly, I suspect the problem lies with the throttle valve or its control system. I haven't heard anything particularly unusual about issues related to north-west damage in this specific vehicle.
haithamina

I hope I've done it correctly this time.

Ulf, could you please take another look at this? Thank you.

chli1976 wrote:

I hope I did it right this time. Ulf, could you please take another look at it? Thank you.

That's good like that.

The log shows a LuMa suction process, then everything runs as it should, and then another suction process occurs -> which is very "nice."
You can see that, similar to the vacuum cleaners, the LuMa/LD ratio decreases starting around 2200 rpm. To achieve this, there must be a bottleneck somewhere behind the LD sensor .
I would actually like to rule out the possibility of a very wide opening (VTG), because according to what I saw on LD-TV, it was already partially open at the beginning of the drama.

As a spontaneous idea, I'm thinking of the secondary air control valve (or EGR throttle valve, if the vehicle has one).

ulf wrote:

As a spontaneous possibility, I'm thinking of a randomly occurring bypass valve, or an EGR throttle valve, if the AVB has such a thing.

Hello.
The shut-off valve seems to be secure, but the EGR throttle valve does not appear to be.
Furthermore, chli1976 has a metal plate to block the EGR system.
haithamina