LMM Failure? Diode Not Working - Need Help!

Hi,
Here's the problem I'm having:
My Passat, manufactured in 1996 with a 1Z engine (90 horsepower and 241,000 km on the odometer), actually runs quite well up to 120 km/h. However, when the speedometer reaches 120 km/h, it simply doesn't accelerate any further, or only very slowly, even when I press the accelerator pedal fully.
So, I went to Volkswagen, and they read the error memory. It turned out there was an intermittent error in the intake manifold. Then they took it for a short test drive while reading the error codes, but no error appeared during the drive.
They then suggested replacing the mass airflow sensor (MAF sensor) just in case, but since I don't want to waste money, I decided to wait and see before spending 100 euros on something that might not fix the problem.
So, I did a little searching online and then I came across this forum, where this is a topic that's often discussed.
Yesterday, I performed a test using a diode (between contact 1 and 6, and the marked side facing contact 6).
When I drove around, it was actually much worse than with the connected mass airflow sensor. It only produced power above a certain RPM, and even then, it was very jerky and felt like it was struggling (around 100-120 km/h). It also didn't accelerate any better.
I'm not sure if the issue might be related to the diode, since I just grabbed one from the basement, but it shouldn't make a difference.
I also read somewhere about disabling the AGR during the diode test. What exactly is the AGR, and where do I disable it?
Could it be that, with 241,000 km on the odometer, the engine simply doesn't have the power to accelerate past 120 km/h? What are your experiences?

I hope a few people read this all the way through and can possibly help me.
Thank you very much.

Tobias.

Hi,

tobias500 wrote:

What exactly is the EGR, and where do I turn it off?

You are currently on one of the pages with the most practical information.
Therefore, one of our common mistakes is "asking first, then reading" - and in terms of AGR, you hit the mark .
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.

Furthermore, was the diode intact and correctly oriented?

Hi,
First of all, thank you for the link... now I know what 'agr' means. However, I had already searched for it myself, but unfortunately, the search includes both headings and content, and since 'agr' appears in thousands of posts, the search wasn't very successful.

Okay, let's talk about the diode: it seems to be working fine, and it's ready for installation. I inserted the side with the marking into contact 6.

tobias500 wrote:

now, regarding the diode: it's okay and ready for installation. I inserted the side with the marking into contact 6.

If the other side was properly connected with a secure connection, it should have worked... If we don't want to just guess randomly, a diagnostic tool like VAGCOM is probably the best way to proceed.

Hello,

tobias500 wrote:

My Passat, manufactured in 1996, with a 1Z engine (90 horsepower and 241,000 km on the odometer), actually runs quite well up to 120 km/h.

However, when the speedometer reaches 120, it simply doesn't accelerate any further, or only very slowly, even when I press the accelerator pedal all the way down.}

I usually experience a faulty mass airflow sensor (MAF) as causing very sluggish acceleration. Conversely, I recognize a lack of power in the higher load and RPM range as a symptom of a clogged fuel filter. How old is the fuel filter? Do you see any black smoke in your rearview mirror? If so, under what conditions?

Best regards, Uli.

I don't actually see any soot.

No, I replaced the fuel filter first, so it's basically brand new.
I think it's weird too, because in the city, speeds up to 60 are actually really good.
Don't you think it could simply be due to age?

Without data from a diagnostic system, we can't go any further here. It could be anything. Emergency mode due to... , lack of boost pressure...

'Unfortunately, our crystal ball is currently being repaired.'

If I were to buy a diagnostic adapter here (I have a laptop), would I be able to determine the values that you or someone else needs in order to provide a more specific assessment?

That's right! The shareware version of VAG-COM should be sufficient for now.