Power Loss: Causes and Solutions (01-11-2003, 21:06)

Hello,
I drive a Golf TDI, manufactured in 1995, with 90 horsepower and 260,000 kilometers on the odometer. It's likely a 1Z model with a wastegate.

'I had the following problem: when I fully accelerated in 5th gear, the car would pull to around 140 km/h and then the engine would cut out (it simply lost power, as if the turbo boost was being reduced). If I then took my foot off the accelerator and pressed it again, it would run up to around 150 km/h, and then cut out again, and so on.'
I had the error codes read (intermittent intake manifold pressure difference), and my friendly VW mechanic said he couldn't pinpoint the exact cause, but he could start replacing parts one by one. Starting with the mass airflow sensor, then the boost valve, and finally the turbo. This seemed like it would be quite expensive, even though he offered to install used parts as a test. I would still have had to pay his hourly rate...

I then worked my way through this forum and came to the conclusion that it might be the boost pressure control valve. So, I got the part and replaced it (it cost 36 euros with the clamps).
But I was unlucky; it wasn't.
Okay, I'll keep reading the forum.
I came across a post discussing the bypass valve on the turbocharger.
Here's how it works: The boost control valve is controlled by the engine control unit. If the boost pressure becomes too high, the valve opens a flap on the turbocharger, and the 'excess' pressure is released into the exhaust.
If this valve is corroded, it can no longer release pressure. To prevent damage to the engine, the control unit reduces the fuel injection amount when the pressure is too high, which throttles the engine speed and thus limits the boost pressure.

The valve was stuck due to rust.
I put the car on ramps so I could access the turbo and the valve from underneath. I sprayed everything thoroughly and then used a long pipe to clear any obstructions in the valve.
It took about 1 hour and two plasters because it was very difficult to access the flap and the supporting structure.
Then I put everything back together and took it for a test drive. Lo and behold, the car runs like new .

I am writing this post to express my gratitude to the administrators of this forum. If this forum didn't exist, Volkswagen would certainly have made a lot of money from me.
Furthermore, I hope that with this post, I can help some people with their problems.

And one more thing: I've noticed that many people ask for advice here and then forget to write back about whether or not they solved their problem, and I don't think that's very good.


Sincerely,
Armin.

Deleted upon request.

diesel.gustav wrote:

Quote: "And one more thing: I've noticed that many people ask for advice here and then forget to write back about how and whether they solved their problem, and I don't think that's very good." That's exactly my opinion too! . . .

I completely agree!
Even if a "problem solved" post may not seem directly relevant at first glance, there are usually many people here (besides the "advice" section) who are interested in the outcome of many stories.

Too often, we have to think, "Ah, he's not writing anymore, so it seems the matter is settled."
Only which tip (often, several solutions are offered by multiple people) then led to the likely success remains unknown .

Deleted upon request.