Loading pressure, VTG, backflow valve... I don't understand anything anymore.

Hello and good evening,

I still have the problem (see also /viewtopic.php?t=17411) that my Golf IV (110 PS TDI, manufactured in 1998) goes into limp mode. The reason for this is a permanently too high boost pressure.
After I checked the functionality using VagCom and had already checked the vacuum lines several times, I decided to purchase completely new lines.
I've installed them today and I'm ready to go. Actually, everything is working perfectly, except that the boost pressure increases slightly (around 0.3 bar) when the engine speed exceeds 3800 rpm.
Wanted to see if the VTG was still functioning (default setting), but nothing happened. The reason was that there was no vacuum pressure reaching the turbo.
Well, so I turned the check valve around, and I had the old problem back. Even at 1500 U/min, the boost pressure is already very excessive, and it does not stabilize (or rather, it stabilizes very, very slowly) even after the throttle is closed.
However, VTG had already moved in its default settings.

Why is it that my boost pressure is actually perfectly fine (target pressure = Istdruck), even though I don't see any adjustments and don't feel any vacuum?
Actually, he should be behaving as if he were in emergency mode, even though he's accelerating perfectly.
I am now completely confused and hope that someone can help me.

Thank you in advance and have a nice evening.

Sven

Hello, I had a similar issue. There was a vacuum hose running behind the diesel filter towards the turbocharger. Check if it wasn't pinched by the diesel filter. I had done an inspection at the time, and after that, the engine was only running at 50 horsepower! Then we checked the hoses and the VTG (Variable Turbine Geometry) could no longer be moved (due to the vacuum). After we had adjusted the filter and re-routed the hose, everything started working as it should again.

As I understand it, you mean the hose that goes directly from the boost control valve to the turbo's pressure housing. I replaced that hose, among others, yesterday. And, as I said, the strange thing is that I'm not experiencing any noticeable loss of power, which is illogical. I'll try driving without the hose later. Was if there was a topic where someone had similar symptoms due to a poorly assembled turbo?

Is it possible that a removed VTG shovel produces so much suction that the turbo becomes uncontrollable, but there is too much pressure when the other shovels also engage?

Space for a tax arm to retract seems to be present in the turbo:


m;

Yes, that's definitely possible. As I said, I found a similar post. I will link it later (I have it at home).
It seems that the adjustment ring was installed incorrectly, which also caused it to get stuck. Unfortunately, I don't have a stage and also no garage, which makes expanding the turbo quite complicated.
However, I have been looking for a used turbo for quite some time.
The turbo now is basically a refurbished one, and you shouldn't really expect such things.

Here is the link: /viewtopic.php?t=4969&postdays=0&postorder=asc&highlight=rückschlagventil&start=24

Unfortunately, the images and logs are no longer available. Would definitely be helpful.

Greetings

Sven

Hello,

ATL with the hanging shovel arms was actually produced from the factory. Some were delivered in this way, but it's moving within the PPM range.

This error can only occur during assembly. Once the ATL has been properly assembled, the "blade arms" will no longer come out of the pockets of the adjusting ring. If your engine was running properly at some point, don't assume that you won't experience problems like the ones you had from the beginning.

Why can the repairman do it better? There are only people working there.

Greetings

Andreas