2.0 CFFB: High boost pressure and rough cold starts

Good day, dear community.

My name is Lukas, and I'm from Kassel or the surrounding area.

Last year, I experienced a major engine failure with my Audi A3 8PA (engine code CFFB). An injector failed, which caused the DPF to glow excessively within a very short time, and then nothing worked anymore.

"Have the car towed to the workshop, where they said the DPF was completely clogged. They could either install a new one or, cheaper – and I'm ashamed to admit it – empty out the DPF."

As naive as I was, I agreed to it.

The engine was running, but it still wasn't working properly. It wasn't until a further inspection that it was discovered that an injector was faulty.

So, this one is updated.

Engine still not running smoothly - turbocharger is faulty!

I replaced that one too... it's still running poorly.

In the end, at least one piston had failed because the glow plug was likely also "melted" or damaged.


Well, I decided to take matters into my own hands. I got a replacement engine and installed it myself.

Since the "new" turbocharger also failed due to previous attempts, a replacement was ordered.
Also, all the oil lines, a new intercooler, and everything else that goes with it.

"However, from the beginning, I've had the problem that it feels like there's a lack of power, it jerks noticeably on cold days until it warms up, and especially under load, the boost pressure is much too high."

All the seals on the EGR system, etc., were also replaced, and the valves were checked for proper function. The intake manifold was completely cleaned, etc.


After the first test drive with VCDS, I didn't really gain much insight. The boost pressure "target" is 2350 mbar, but the actual value sometimes exceeds the measurement range of 3000 mbar.

So, I used a T-connector and checked the vacuum pressure with an analog gauge, and I found that it was partially stuck between the N75 valve and the VTG (variable turbo geometry) control unit.

After a lengthy search, it turned out that the hose had become very soft due to the heating and high temperatures from the DPF.

At least the problem almost disappeared immediately when I started using Festo hoses for testing.

However, the boost pressure was still inexplicably high in some places.

The vacuum sensor is optimally adjusted, with a pressure of approximately -0.65 bar and a voltage of 0.76 V.

"Adaptations and all necessary adjustments have been made multiple times, and according to VCDS, they have always been successful. However, the boost pressure still occasionally reaches 2600 hPa."
Often it adjusts to the desired setting, but sometimes it doesn't, and the heating element symbol appears.


I've also replaced the mass airflow sensor again (with an original part), but the problem just won't go away.

I'm slowly reaching the end of my rope.

I've also ordered a kit to check the charge air cooler system for leaks. My current thought is that there might be a leak somewhere, which is why the engine is working so hard to compensate and reach the desired boost pressure.

Here's a log from last year, before I replaced the soft vacuum hose (pressure up to 3000 hPa).

and one from yesterday after replacing the mass airflow sensor.

What also surprises me are the discrepancies between the intended and actual air mass values, as well as the boost pressure itself, even when the engine is idling, sometimes reaching 1300 hPa while the target value is supposed to be 1000 hPa.


Let me know if I need to do any more trips with other vehicles. I'll do everything necessary to get it working properly again.


Thank you for reading.

Lukas.

Edit: The N75 component has already been replaced.
What's still missing is the boost pressure sensor, but since I had major back surgery at the beginning of the year, I'm a bit more cautious about getting under the car.

Hi there,
By performing an automatic scan and, most importantly, by entering your license information into your profile, it would be possible to help you troubleshoot the issue. So far, you've been trying to fix the problem by replacing expensive parts. This is a wasteful use of money (yours).
hg
Herbert.

Hello Herbert,

I'm new to this forum and still trying to figure out where to post things.

My VCDS is from PCI ROSSTECH, can I integrate it?

I will do that as soon as I get home.

"An Autoscan wouldn't be helpful right now because the error indicates that the memory is empty. However, I'll check if I have any old error messages saved."


Roughly speaking, that's what it said.

Boost pressure exceeded.
Turbocharger stuck.

But it's a brand new loader, and it's purely mechanical – even if the turbo is hot, nothing gets stuck. You can test it with diagnostics, and it reaches all its end positions within the specified range.

I'm not quite sure about the trip details.
At one point, you can observe the boost pressure request increasing. The wastegate (Vtg) adjusts to direct flow towards a lower raw voltage (indicating low voltage). The charging pressure increases, and the request decreases. Then, the raw voltage increases again (so the Vtg moves), and even though the target boost pressure of 2350 mbar has already been exceeded, the request continues to rise, causing the Vtg to adjust towards higher pressure.

Not plausible for me.

The system detects that the boost pressure has already been exceeded, but sometimes it doesn't counteract this (via the variable turbine geometry).

Hello Lukas,
It is what it is; this forum is run by the homeowner and entrepreneur of https://shop.dieselschrauber.org/en/. Without his financial and personal investment, this forum would not exist. With VCDS from PCI, you've ended up with the competition. This might not be a major setback for you, especially considering the previous damage, but I assume that a "support key" is helpful here for support. The terms of service and the homeowner will provide more details.It will definitely continue.
hg
Herbert.

Whether you can believe it or not (I'm still very confused myself)... The error has been fixed, and everything is working properly again .

Hello,

der Lader repariert sich nicht selbst, wenn er hakelt wird Dich das früher oder später einholen.

In the past, faulty mass airflow sensors (MAF) often measured excessive air intake, causing the engine control unit to aggressively attempt to achieve the target values, which resulted in misfires and power loss.

Sure, here's the translation:

"This is just for background information."

If your problem catches up to you, feel free to continue using VCDS or a support key.

Best regards, Rainer.

He didn't write about what the cause was, did he?

At that time, he couldn't, because the thread had been closed for a long time .

It seemed that the boost pressure sensor was the culprit, as it appeared to be relatively oily. That's what he thought at the time, anyway.

After the replacement, the car ran perfectly with the correct boost pressure and performed as expected for several trips, which it hadn't done before.


But it seemed to be just a coincidence. Because the charging pressure is still occasionally exceeded.

Just the other day on the highway – going up the Kassel mountains at 130 km/h. It had been running at 1.5-1.6 bar for too long.

However, the performance feels significantly too low at those moments. It definitely doesn't feel like he's using a realistically high level of difficulty (LD).

Some days, it regulates perfectly and quickly, reaching a value of 1.35. However, it still feels "sluggish."

I'm now at the end of my rope with this, and almost at the point where I'll just accept it .

Quote:

Es war am Ende *vermeintlich* der Ladedrucksensor welcher relativ ölig war. So dachte er es zumindest damals.

It's perfectly normal for the turbocharger pressure sensor to be oily.

Debugging is sufficiently described; simply follow the steps.
Okay, I'm ready. Please provide the German text you want me to translate into English.