AFN Engine: Sudden Power Loss at 120-140 km/h

Hello, I'm having the following problem:
Golf 3 TDI 110 HP MK:AFN. Excellent acceleration in every gear and at every RPM, but above 120-140 km/h, the power suddenly drops, as if it were a naturally aspirated diesel, regardless of the gear. This problem can only be resolved by briefly turning off the engine, and it reappears after about 5 seconds while driving at that speed. I've also noticed that whenever this happens, the control rod on the turbo goes completely down, and the vacuum from the hose connected to the turbo control valve drops. If I disconnect the connector from the valve where the hose is attached, the power is always lost. Is this due to the valve, the engine control unit, or something else?

Please help me, I don't want to always just drive at 120 km/h...

Hi,

Try using the search function, for example, with the term "Notlauf".

The technical articles about the VTG loader and about VTGs that are stuck might also be helpful to you.

I've now loosened the adjustment rod on the turbocharger housing so that the boost pressure was significantly reduced, and the error still appeared unchanged at 120 km/h.

What else could it be?

I've now loosened the adjustment rod on the turbocharger so that the boost pressure was significantly reduced, and the error still appeared unchanged at 120 km/h, repeatedly.


Okay, I don't want to complain or anything, BUT: If you simply change the length of the rods significantly, then it's clear that the emergency mode will be triggered based on that alone. The control unit will then try to build up pressure, but it won't be able to do so because of the rod you adjusted. The consequence of a significant pressure deviation is: emergency mode!

What about the issue of difficulty of movement? Have you read the technical article on VTG?

I already know that whenever this happens, the control rod on the turbo goes all the way down, and the vacuum from the hose that goes to the turbo control valve drops.
Okay, sure! In emergency mode, the engine control unit (ECU) disables the turbocharger control to protect the turbocharger. It doesn't matter whether the turbocharger itself or something else entirely was the cause of the emergency mode.

Is it due to the valve, the control unit, or something else entirely???
It could be due to something completely different, but it doesn't necessarily have to be.


Okay, first, turn the VTG shaft to its original length (hopefully you've marked it!). Then, read and follow the technical article on systematic troubleshooting for TDIs. After that, post the results and standard details (tuning?, smoke?, were any changes made before the error occurred?), and ask any questions if needed.

Regards,
Private.

It's almost embarrassing to say, but: read the error codes. Who says it's related to the turbocharger pressure control?

Best regards, Rainer.

I used my shareware software, VAG-Com, to read the error codes, and it couldn't find anything, even after it went into limp mode again.

Since you apparently have a VAG-COM interface and adapter, please read the technical article on systematic troubleshooting with VAG-COM and then post the measured values. https://community.dieselschrauber.org/en/viewtopic.php?t=3322

I haven't heard of an emergency landing happening without any error messages being recorded.

Regards,
Private.

But with VAG Com Shareware, I can't read out any measuring blocks, right? Or at least, I haven't found that feature yet.

But with VAG Com Shareware, I can't read any data blocks, right? I haven't found the option yet.

Sure, I can!

01 = Motor
08 = Measurement data block.

Are you sure you actually tried to read any error codes? Was the ECU identification number read correctly? I still can't get rid of the limp mode even though there are no error codes.

Regards,
Private.

He always just writes: 'Mass failure, preheating lamp.' But that's definitely broken, so it can't be the problem, right? And below that, he always writes 'Shareware version, please unlock!' three times. How do I read the data blocks? I can only go to 'SELECTION MENU' in the upper left corner, and then it shows me something like '01 ENGINE ELECTRONICS.' I click on that, and it reads everything. Then I can only display and delete error codes, but I don't have a '08' at all, for example. And how can I check the MAF sensor? I know I need to compare the actual values (IST) with the target values (SOLL) under load, but where can I see the actual values?

Best, Chriss.

Okay, I found it. Yes, you really need to familiarize yourself with it before complaining! So, he found 3 errors, but he couldn't identify 2 of them because they were only present in the shareware version.
Error 1: 0741.
Error 2: 0575
Error 3 (glow plug): 0626.
Tax device no. 00 SG 1444.
VAG NR. 028906021GH

I also found information about the measurement blocks. Is there an article that explains what these things are?

Thank you,
Best regards,
Chriss

Okay, one more question: I'd like to order a power box. Which one should I get, the one that plugs into the pump or the one that plugs into the control unit?

Best, Chriss.

He wasn't looking, but others found it for him.

/viewtopic.php?t=449&highlight=error+741

As I said: first, clear all the values, drive until the 120 km/h error appears, then read the values again to see what is actually set.

"Bremspedalschalter" sounds good, then he means you would be braking all the time and he "doesn't want" to drive faster .

You probably set the 575 yourself through your VTG experiments.


To the boxing ring.

"BOX" already indicates something about the principle of operation (where it's located doesn't matter). With a "BOX," you create a separation from the Electronic Control Unit (ECU) compared to a "CHIP."

May he be able to read and understand this.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Or, ideally, read and understand all the relevant articles first .

Hello, so I've just taken the following tests:
'I disconnected both brake pedal switches, and now the system no longer throws error code (741).'
2. I've deleted all the error codes, and every time I exceed 120 km/h (approximately 75 mph) and it goes into limp mode, it displays the code 575.
3. In measurement block 10, columns 2 and 3 remain unchanged regardless of the load condition, always displaying the value 1010 in both columns.
'In measurement block 11, the second column shows what I believe is the target boost pressure, while the third column always displays a constant value of 1010. Is this the actual pressure? Could it be that the boost pressure sensor is defective, or whatever it's measuring?'


I would like to replace the magnetic valve for boost pressure limitation, where is it located?

Best, Chriss.

Rasergruening wrote:

4. In measurement block 11, the second column shows me the target boost pressure (I think), and the third column always shows 1010, unchanged. Is that the actual pressure? Could it be that the boost pressure sensor is defective, or whatever it is measuring?

Yes, the third value represents the actual boost pressure.
Possibly, the thin hose between the intake manifold and the engine control unit (where the pressure sensor is located) is leaking, blocked, or disconnected.

I would like to replace the magnetic valve for boost pressure limitation due to the 575 issue; where is it located?

That's unnecessary information for now. Regardless of what faults the solenoid valve might have, the turbocharger should always build up some pressure (even in the 'no pressure' solenoid valve position).

Since you're always measuring ambient pressure, something else must be wrong. Please review Ulf's post.

To fully answer the question: It's located at the other end of the thin hose that leads to the turbocharger...

Regards,
Private.