Boost control solenoid valve. Power loss (A3 TDI)

Hello,

'I also have the problem of power limitation (due to the engine's limp-home mode) on my TDI (Audi A3, 90 hp, manufactured in March 1998, engine code: ALH, VTG turbocharger), starting around 2800 rpm (it initially started around 3500 rpm).' The Audi workshop says the turbocharger pressure is too high due to a faulty turbocharger and wants to install a new one for me, costing around €800... which I politely declined.
The VTG (Variable Turbine Geometry) linkage for adjusting the guide vanes is movable (verified by turning the valve on and off at idle => movement is possible over the full range). However, I haven't been able to test how easy or difficult it is to access yet, unfortunately, due to the 'user-friendly' design of the charger's installation.
A new lambda sensor has already been installed (approximately €270;)), which, while addressing a different issue (the engine only delivered power intermittently after pressing the accelerator, then running in limp mode), did not resolve the actual power loss at higher RPMs.
My suspicion is now leaning towards the solenoid valve. It seems to be okay electrically, but what about mechanically? In the forum, I read somewhere that the part is supposed to cost 30 € [b]. But where? [/b] My Audi dealer told me it should cost 106 €.
Could it possibly be due to the boost pressure sensor? Where is it actually installed?
The error log only showed 'Mass airflow sensor values are implausible' (see above).

Thank you very much!

Regards,
Peter.

Hello,

Before you replace everything, you should perform or have someone perform a measurement run. The ALH values are in the error database.

When you have a performance test carried out, you should pay close attention to ensuring that the conditions for idle and full-throttle measurements are met (including in the error database).

Peter wrote:

...My suspicion is now leaning towards the solenoid valve. It seems to be okay electrically, but what about mechanically? In the forum, I read somewhere that the part is supposed to be available for 30 €. But where? My Audi dealer told me it should cost 106 €.

Hi,

Your dealer is correct: the part has the number 1H0 906 627A and costs 106.49 EUR .
A similar part is used for the AGR (Active Grille Release) system (part number 1H0 906 627) and costs approximately 79 euros.
I can't tell you what the difference between the two things is, but I also recently encountered that expensive solenoid valve...
For the 1Z, the part (which is smaller and has a different connector) costs approximately 30 euros.

Hi,
Then I suppose I'll have to dig a little deeper into my pocket if further investigations point to the valve as the cause. I currently have some requests pending with spare parts search services, so let's see what results they come up with...

Since there's no way to diagnose the problem myself, I have to have the diagnostic test performed, and then I won't have any influence on the investigations. Unfortunately, so far I haven't had direct contact with the technician who examined my car at the Audi workshop, but only with the customer service representative.
I guess I'll have to visit another workshop, maybe a smaller one that specializes in engines, and I'll tell them about my findings and yours.

Thank you and best regards!
Peter.