Hello,
I was hoping I could get some help troubleshooting a boost issue that just came up on my 1999 1.8T. The car was driving fine the night before, and then yesterday when I started it up and started driving, I couldn't get past 0 psi and obviously the car is extremely sluggish.
I'm getting good vacuum so I don't think it's leak in any of the lines.
There aren't any CELs, Vag-com is only showing a code for the throttle body that's been there for years.
My initial thought was that it was the N75 valve, so I removed the line from the valve to the wastegate to test it and still no boost.
The turbo only has 10k miles on it, bought it new from G-pop shop.

I'm really hoping my turbo isn't already shot, but it's hard to tell if it's spooling. What else could it be? Wastegate stuck open?

Any tips for what to look at next?

Mike

 

The wastegate (or whatever our equivalent is called) being stuck open sounds very possible, but you could also have a leak somewhere between your turbo and intake and (if I'm not mistaken) I don't think that would affect vacuum.

You can test everything but the air box, by removing the intake tube from the air box and sealing it up around some kind of compressed air nozzle. Set the pressure on the compressor to a few pounds more than your turbo makes and if it holds that pressure (with the engine off) then you know that your piping, intercooler and all related parts are good, eliminating those possibilities, which would bring you back to the turbo and/or the wastegate being the culprit.

LMK how it goes and G/L

.

 

So here's a quick update that may help further define the problem.

I haven't had time to work on the car but have to keep driving it since it's my only mode of transportation.

After taking it on the highway, the car will make 1psi at WOT, until about 5500rpm it can make about 5psi. This makes me think that the turbo may not be seized, and that it's a wastegate or hose problem. I'm hoping to test both of these soon. Does anyone else agree?