Passat 1.9TDI (130hp) turbo nos kicking in

**edugimeno** · 11-11-2020,08:05 PM

Hi there!
I own a 2002 1.9TDI Passat (130hp) and since 2 months ago the turbo is not working at all.
It started intermitently, but recelty there's no turbo kick at all. It's like driving a 50 hp car...

My tests:
First I suspected the vacuum lines feeding the turbo discharge valve. I manually moved the discharge valve rod and I feel it's not quite smooth. Could this be enough?? The I tested vacuum while my wife was accelerating and there was no vacuum at all at eh pipe controling the discharge valve.

So I suspected the lines and the N75 valve. I disassembled my N75 valve and internally all looked good. Clean and smooth. The membrane was perfect, the rod was sliding very smoothly inside, the in/out/discharge ports were clear....But I tried to test its functioning by manually applying vacuum to the in port while appliying 12V to the plug, and no changes were appreciated, aht vacuum was in both cases routed to the same (center) port. This led me to think the N75 was bad....

Then I bought an used N75 and new vacuum lines. I first tested the N75 and unexpectedly got the same result. Vacuum always routed to the 2nd port with and without 12v. I could feel it moving inside but the expected effect was missingg. Maybe my test procedure wasn't working?

Anyway...I indestalled the "new" N75 valve and the new vacuum lines. Nothing. Still weak, no turbo.

Then I realized somethign I should have done before, plug my Delphi box. I thrw a "17564 - Manifold Pressure Sensor: Short Circuit ro Ground or Open Circuit / Intermitent". Maybe I am looking at the wrong place? I tried to erase the DTC but it gets back instantly, all the time.

I have ordered a new MAP sensor, but in the mean time Im wondering if this could be the cause. Is the ECU not requesting the turbo to kick in? How can I really test the N75 valve? I kind of understand all the vacuum circuit but I really don't see whi there's a 3rd port in the valve, I don't know if while accelerating on neutral the turbo would be expected ti kick in, if the little resistance in the turbo discharge valve rod would be enough to prevent it from moving.... So many questions...

Anyone has any idea on what to test first?

Thank you!