Help!! Boost issue??

[Midnight toker]

Yesterday the car ran fine. Today I started it up to go to the gas station noticed nothing different. As I pulled out and started to go down the road I noticed that the car was not building boost. So I gave it some throttle and the Turbo spools and build boost when it wants but Cuts back out. I don't know what's going on the car has power when it wants to and other times it's no boost. And I went over the car with some carb cleaner to try and find a vacuum leak but found nothing I need help it's a 2002 C5 A6 2.7 t

[Midnight toker]

I also have a boost gauge usually I run around 10 PSI boost and 20 vacuum. But I noticed today that the car would spike 215 back down to 10 and bounce around and also the vacuum is now at 10 and not 20

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I also have a boost gauge usually I run around 10 PSI boost and 20 vacuum. But I noticed today that the car would spike 215 back down to 10 and bounce around and also the vacuum is now at 10 and not 20

[ShelbyM3]

Sounds like you have a boost leak somewhere. Throttle body boot is a common source. It’ll tear on the bottom side where you can’t see.
Do you have a way to check for CELs?


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[Midnight toker]

I do not

[C5S6]

I had a breather fitting/hose pop off the back of the intake manifold twice. After the 2nd time I secured it with a zip tie. Car behaved as you describe both times.

[Midnight toker]

Had it read via vcds. Codes were for a secondary air injection and something about a boost valve?

[Freddieb23]

Had a similar issue with my 14 S6, I had a bad catalytic converter,

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[ShelbyM3]

Secondary air is common and will require attention, but not crucial to performance.
Boost valve could maybe be N75. That controls your wastegates.


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