Sudden Loss of Power at High Speeds

Hello,

I have a problem. I hope you can help me.

'When I'm driving in 5th gear (sometimes even in 4th) and I floor the accelerator, it pulls strongly at first, but then suddenly (usually around 120 km/h) it stops accelerating as if I'm letting off the gas. Only when I briefly release the accelerator does it continue for a moment, until the whole thing starts again.'

The strange thing is that he manages to complete the lower gears well.

Please give me some tips!



PS: It's a Volkswagen Golf III Variant TDI (90 hp).
with cruise control (if that might be relevant).

Please try searching using terms like "wave-like acceleration" or similar.

Furthermore, various specialized articles also contain information about these symptoms.

If you get stuck, you can ask more specific questions and explain which potential error sources you have ruled out and what steps you have taken.

Regards,
Alex.

I took a look at the mass airflow sensor earlier, but I couldn't really see anything.

Do I need to take it apart, or is there no way to tell if it's still working?

You should read the technical articles on troubleshooting and mass airflow sensors.

Okay, I was just at the workshop and had the error codes read.

Two errors were detected.

'17978 P1570 035'
Engine control unit locked.

00575 017
Intake manifold pressure.
Rule difference.
sporadically


The mechanic also tapped the mass airflow sensor.
However, it would cost 50 EUR just to test the mass airflow sensor.

That was a bit too much for me.

Earlier, I also injected some industrial cleaner into the mass airflow sensor (MAF sensor), which is the Pierburg model.

However, it didn't achieve anything.


Unfortunately, I don't have a laptop to check the LMM myself.
Is there another option, or perhaps someone nearby who offers this service at a reasonable price, or maybe someone who would lend me a language model (LLM) for a short time in exchange for a few euros?

What do you think about these error codes?

Hello,

Just try entering 'intake manifold pressure' as a search term.
Furthermore, as a minimum, one should include their MKB (German tax identification number) with the relevant information.

Thank you for the tip.
I'm new here and I've only had my Golf for 2 weeks.
I'm sorry if I'm not writing ideal posts yet.

I've found something now:

Symptoms: Intermittent or constant lack of power in some or all engine speed ranges, occasionally accompanied by surging or wavy acceleration.
Full power is sometimes only available for a short time after the engine is started or when the accelerator is released.
Occasionally, error messages such as 'Intake manifold pressure control differential' or 'Forced induction pressure control exceeded limit' may appear.
Boost pressure indicator (if available) shows unusual/incorrect values.
Common causes: Faulty boost pressure control or turbocharger .



Is it likely that the air mass sensor is the problem in my case?
Take a look at the turbo for me later.

Should I have an AFN? (Golf III TDI 90PS)

Hello,

Either your horsepower (90) specification or the engine code is incorrect.
Der AFN hat 110 PS, schau doch noch mal nach. Then you can.
to provide further and proper assistance.

You are right, I have a 1Z.

Try the trick with the diode (search function 'Diode Lmm'). Then you can rule out the LMM if nothing changes...

@All: Yes, yes, I know I suggest the diode number every time, but I think it's so great . The potential for savings is simply enormous...

Okay, now I have to ask some silly questions again:

I hope you are kind enough to answer them anyway.
I have now found several posts that perfectly match my error description.

I want to check the turbocharger's shaft and the magnetic valve.
Unfortunately, I haven't found either of them.
I know roughly where the rod is located, but it's quite difficult to access.

Do I have to look from below?

Where is the solenoid valve, and is there a way to test it?


Okay, here's the translation:

'So, please help a beginner.'

Hello Alex!

You're driving a 1Z engine with a turbocharger equipped with a wastegate. In this setup, the pressure sensor for controlling the wastegate is located underneath the turbocharger's compressor housing. The linkage is practically invisible from above and extremely difficult to access.
If the car is raised from the front and the lower engine cover is removed, you'll have a very good view of the turbocharger, including the pressure sensor and linkage.

But be careful: Do not confuse this with the adjustment rods for the VTG (Variable Turbine Geometry) system! You have a wastegate turbocharger! If you adjust the length of the rod incorrectly, you could prevent the wastegate from closing. In that case, you will practically no longer build up any pressure!

The solenoid valve should, in my opinion, be mounted on the 1Z engine, in the area of the upper engine cover, towards the intake manifold on the engine block (who knows better?). From there, a hose runs directly to the intake manifold (before the turbo), another to the pressure side of the turbocharging system, and one directly to the pressure sensor of the turbocharger.
As a simple test, you can first measure the resistance with a multimeter while the plug is disconnected. It should be between 25 and 45 ohms.
If you are driving with the boost pressure sensor disconnected, the maximum boost pressure should be approximately 0.6 bar (check using VAG-COM or LDA). If this is the case, it ensures that the valve is not stuck.
With the connector plugged in, the target charging pressure should be approximately 0.9 bar (above 2500 RPM and under full throttle).
If that is the case, then your boost pressure control system should be working correctly.
If that doesn't work, try replacing the solenoid valve (as a test?).

Regards,
Alex.

Thank you for the detailed answer.

Unfortunately, I don't have any way to check the boost pressure.
Our VW workshop isn't very competent either.
(I think 50 EUR for a test drive just to check the mass airflow sensor is quite expensive.)


But now, let's get to my theory:

When I disconnect the solenoid valve, I always get a pressure of 0.6 bar.
So, I would generally have slightly less power, but in return, I shouldn't experience that drop in performance at 120 km/h anymore.

I wouldn't be able to tell if it's the solenoid valve causing the problem.


I also tried disconnecting the MAF sensor once, but then I couldn't reach 120 .

Hello Alex!

Quote:

When I disconnect the solenoid valve, I always have 0.6 bar.

Only if the valve is working properly or is stuck in a "safe" position.

However, if the valve is stuck in the other position, the wastegate valve will no longer be activated, which means your boost pressure will no longer be limited.
Then, if the boost pressure is too high, the engine management system intervenes and reduces the fuel injection amount in order to reduce the power output of the turbocharger.
That might be the case for you. Does your engine then actually go into emergency mode (does the preheating indicator light up)?

Try driving with the connector unplugged and then post the results here.

Regards,
Alex.

Okay, I just did a test run with the connector unplugged:

- I have to say, I didn't notice the slightest difference.
- I also measured the resistance of the solenoid valve: 15 ohms.
- Indicator lights are not illuminated.

One more question, just for clarification:
What do you think, can I start to hope that the LMM is no longer a viable option? (I don't want to spend 200 EUR).

You can rule out the HFM/LMM if you have already checked it. We're not really in a situation where we can afford to take risks here.