1Z Power Failure: Troubleshooting Guide

Hello,
I'm a bit lost at the moment...
'On my Golf III TDI (1Z) with 170,000 km and without any chip tuning, the following error occurs:'
575 intake manifold pressure.
Additional information from the control unit regarding the error code: Intermittent control difference.

VW workshop stumped... Mass airflow sensor (MAF) replaced, but the problem persists. Fuel injector replaced 2 years ago due to TDI engine misfires (which was fixed at the time). Turbocharger replaced (suspected stuck wastegate), pressure hoses renewed.

The boost pressure gauge indicates the following: Under load on the highway, the boost pressure increases to 1.3 bar, then the control unit regulates it back to 1 bar, resulting in a loss of power.
Normally, the boost pressure should be regulated at 0.8 bar by opening the wastegate valve. I've already checked that the pressure hoses were connected correctly by the workshop. In my opinion, the problem is not with the engine control unit, because it initiates a power cut at a boost pressure of 1.3 bar.
Since the new turbocharger was installed, something strange has been 'rattling' under full load (i.e., when the turbo kicks in).

I'm really drawing a blank... The technical articles aren't helping either.
Who has advice?
Despair...
(I'm going to shoot the next VW mechanic to the moon!)
Regards,
Vasmodis!

Hi,

The wastegate of the 1Z engine opens at 0.6 bar. Using a bypass circuit (boost control valve), the pressure acting on the wastegate is reduced, resulting in an effective boost pressure (intake manifold pressure) of approximately 1 bar. Overboosts are possible. However, 1.3 bar seems quite high.
I would try replacing the turbocharger boost control valve (located in the engine compartment near the diesel filter). It's not very expensive, and it has been known to fail in 1Z models before.

Hi!
Thank you for your reply.
I replaced the lead pressure control valve 2 years ago (as I mentioned before, it was causing the TDI to jerk).
Since it's 'relatively' new and the symptoms were different back then, I ruled it out. But you're right, it's not that expensive, so it's worth a try.
Are there any other potential sources of error?
Regards,
Vasmodis!

Hi, so, regarding the error message about the intake manifold pressure, it's probably the boost valve. And about the other error message... I had that one once too. The VW mechanic said it might happen again, and then it would be necessary to replace the ESP (Electronic Stability Program) module, or the mass airflow sensor might be defective. I have no idea if it can be repaired.

Best regards,
mhernach


Hello,
I'm a bit lost at the moment...
'On my Golf III TDI (1Z) with 170,000 km and without any chip tuning, the following error occurs:'
575 intake manifold pressure.
Additional information from the control unit regarding the error code: Intermittent control difference.

VW workshop stumped... Mass airflow sensor (MAF) replaced, but the problem persists. Fuel injector replaced 2 years ago due to TDI engine misfire (which resolved the issue at the time). Turbocharger replaced (suspected stuck wastegate), pressure hoses replaced.

The boost pressure gauge shows the following: Under load on the highway, the boost pressure increases to 1.3 bar, then the control unit regulates it back to 1 bar, resulting in a loss of power.
Normally, the boost pressure should be regulated to 0.8 bar by opening the wastegate valve. I've already checked that the pressure hoses were connected correctly by the workshop. In my opinion, the problem is not with the engine control unit, because it initiates a power cut at a boost pressure of 1.3 bar.
Since the new turbocharger was installed, something strange has been 'rattling' under full load (i.e., when the turbo kicks in).

I'm really drawing a blank... The technical articles aren't helping either...
Who has advice?
Despair...
(I'm going to shoot the next VW mechanic to the moon!)
Regards,
Vasmodis!

Vasmodis wrote:

Are there any other potential sources of error?

Hi Vasmodis,

Remove the solenoid valve and replace the hoses (they are quite cheap for VW -> 11 euros per meter ). It's a good idea to replace them at the same time . Even a small hole in the hose can cause these symptoms (I experienced this with my Passat 1z and my father's 1z ).

Which solenoid valve should I replace?

best regards

Are there any other potential sources of error?


Hi Vasmodis,

Remove the solenoid valve and replace the hoses (they are quite cheap for VW -> 11 Euros per meter ). It's a good idea to do this at the same time . Even a small hole in the hose is enough to cause these symptoms (I experienced this with my Passat 1z and my father's 1z ).

mhernach wrote:

Which solenoid valve should I replace ==?????

for boost pressure limitation?

... and maybe check if the wastegate is stuck or corroded.

Best regards, Rainer.

That's the solenoid valve for the 1Z engine.

I have the control unit mounted above it, but it's secured to the fender with a rubber buffer and it's rattling around there.

m;

Sorry, but on my Galaxy, it's located right next to the diesel filter.



This is the solenoid valve for the 1Z.

I have the control unit mounted above it, but it's secured to the fender with a rubber buffer and it's rattling around there.

m;

Hi,

mhernach wrote:

Sorry... but on my Galaxy, it's located right next to the diesel filter...

What do you think that thing in the picture is, above the marking? It's the diesel filter! (It's unfortunately hard to see).

By the way, I described the situation earlier in the text.

Bertil wrote:

I would like to replace the turbocharger boost control valve (located in the engine compartment, near the diesel filter).

I replaced the magnetic valve for the boost pressure limiter today... and there you go, it works again!
The cost is 35 euros, which is ridiculous, especially considering that Volkswagen would have charged approximately 700-800 euros for the repair.
This is already the 3rd solenoid valve. I replaced the 2nd one about 2 years ago due to a TDI engine misfire, which was resolved by the replacement. That's why I initially ruled it out as the source of the problem, as the symptoms were completely different.
I have to say, it's a real disgrace for the VW workshops that, after replacing the mass airflow sensor and it not fixing the problem, they wanted to replace the turbo (suspecting a stuck wastegate).
Okay, thanks again for your help!
Regards,
DOC!

Vasmodis wrote:

This is already the 3rd solenoid valve. I already replaced the 2nd one 2 years ago due to the TDI engine misfire, which was resolved by doing so.

Hi Vasmodis,

How is the TDI shudder related to the solenoid valve ?

How does the TDI shudder relate to the magnetic valve

Good question...
That was one of the tips I received two years ago, after two (expensive) visits to the workshop, when the annoying jerking during acceleration on the highway still persisted, despite replacing the mass airflow sensor and other things.
The top speed back then was 130 km/h, but that was only achieved with a 'jerky' engine, meaning it was like taking your foot off the gas and then pressing it back down.
Replacing the magnetic valve for boost pressure regulation, as shown in the photo above, fixed the problem at that time. However, recently, the problem of engine shutdown at approximately 3500 RPM (or reaching the shutdown pressure of 1.3 bar) has reappeared in the 4th and 5th gears. These were completely different symptoms, so my first thought was definitely NOT the magnetic valve. The VW workshops then replaced the mass airflow sensor (MAF) (although it was also only two years old, and it was reinstalled after the error persisted at my urging) and told me that the wastegate of the turbocharger was stuck, which would require a replacement (the price for the turbocharger was 700 Euros, and the labor cost was estimated at 300 Euros ).
I then bought the turbo myself (new, for 468 euros from Turbo Twins) and installed it, replacing all the pressure hoses at the same time. The error still occurred *sigh*...
Okay, so there weren't many options left... it was either the solenoid valve or the control unit, and I definitely wanted to try the cheaper option first.
Long story short...don't trust any VW workshop...
Regards,
DOC!

http://members.aon.at/turbotwins.at/

Hello everyone.
After 2 years of searching and having driven tens of thousands of kilometers (that's true passion for the Passat).
'I replaced the solenoid valve today because I found the symptoms of my problem described in this post.'

It's finally running smoothly again without any jerking or loss of power!
THANK YOU TO EVERYONE WHO POSTS SUCH HELPFUL AND INFORMATIVE INFORMATION HERE!
YOU ALL DESERVE A BOTTLE OF CHAMPAGNE.
(please do not use while driving

For your information: On my Passat (35i facelift, manufactured in 1994, engine 1Z), the solenoid valve is located on the right side of the coolant expansion tank. To help you find it, I've included a picture here:


http://www.auja.de/img/magnetventil.jpg

Thank you again!
Greetings to Rainer, Ulli, Haenlein, and Bertil, and all the other mechanics .

Please don't yell at me, but are you referring to the wastegate valve when you say 'magnet valve'? I'm having a problem (Golf IV, AXR TDI PD) where it makes a strange hissing/chattering sound when I release the accelerator. I've read that this could be due to a faulty wastegate valve that isn't closing/opening properly.

Can you help me with that? Specifically, where it is located and how much it costs?

Best regards,
VipViper2000