How much vacuum should I have?

[Adal2154]

2005.5 jetta I'm having a p0299 code car goes in to low power mode randomly.
If I turn off the car and back on its fine.
I have replaced the n75 after sending Malone a log he said the Gaines are not closing but its trying sill does it
I tested the waster gate actuator with my mighty vac holds at 20 for quite some time I left it for a few hrs and it dropped to15
I have checked all inter cooler lines they are tight

I put a t in the line from n75 to waste gate and I put a vacuum gauge on it it pulls 20ish on start up but then settles at 8-10 car seems to boost to 12psi

When the car goes into low power mode the vacuum goes to zero and the boost stays at zero

Any suggestions I do have a vcs if there's some readings I should take

 

[740GLE]

Looks like you pegged the issue being vacuum related.

I don't know the proper values you'd expect at idle but, I don't think at anytime it should ever go to zero (there goes your power brakes!) I'd start checking for leaks and cracks on hoses and start replacing everything as systematically as possible.

 

[Adal2154]

Well it's only going to zero going to the waste gate from the n75
What controls that is basically what I'm trying to figure out I guess
What tells the n75 to dump the vacuum

 

[Mechnurse]

The ECU, it allows for a little deviation from the requested boost. When it doesn't meet this request it causes limp mode and may turn on the check engine light.

 

[Adal2154]

Now I know on my dodge cummins I can just permitly keep the waste gate closed and it does not cause any issues has anyone done with with this car or is it a bad idea

 

[gquenstedt]

Your car doesn't have a wastegate. It has a vane actuator. So, when there is no vacuum, you'r turbo doesn't make any boost. When there is vacuum, it actuates the turbo, and you get boost.

Look at the valve cover of your engine. In the back, there is a vacuum line connected to the valve cover. Pull it off there, and try to draw vacuum at that point. That is the vacuum reservoir, so it should hold vacuum. If it doesn't, that could be your problem.

 

[Adal2154]

Ok thanks for the input that's what I mean by waste gate if I make it so the rod stays extended what would it do I have 20 psi of vacuum at start up then it settles at 8 and it went into low power mode last night and its def loosing vacuum bc most the day vacuum was at 3-4 like it slowly looses vacuum but if I restart the car it comes back but not as good as it is on first start up of the day should I just start replacing the lines?