: Boost not building sometimes

2012 CTS-V
04-20-13, 04:36 PM
Hey guys so sometimes my boost is not building. If my car is running well the boost gauge will read 12 psi. I went out for a ride before and it wouldn't go above 5 psi. Any ideas? I have an automatic 2012 sedan with upper pulley tune thermostat and intake.

04-20-13, 07:01 PM
I just had the same issue with my 2009 MT with similar mods. Two possibilities I was told to look for were belt slip and also the boost bypass valve. Turns out it was a combination of both. To the left of the actuator on the bypass valve there is stop bracket with a set screw. If the bracket is not adjusted right or the set screw is in to far, the butterfly valve isn't completely closed and you are bleeding off boost. In my case the bracket was misaligned (should be straight up and down) and the butterfly was staying open. Also belt slip becomes an issue if you do not have an idler pulley which I will soon be adding. Hope that helps.

2012 CTS-V
04-22-13, 12:33 PM
Thanks I'm bringing my car to my tuner this week. He mentioned it might be belt slip but has to take a look at the car. I will mention to him the issue you had with the boost bypass valve.

04-22-13, 01:46 PM
It is going to be the bypass valve, just look and do the pvalve mod, it is the easiest.. It will still shut off boost while non full throttle, so you don't have to worry about anything. It will just not be able to pull boost anymore.

the blur
04-28-13, 06:06 PM
My 2009 is all stock , and the boost gauge only goes about 1/2 way. Is that normal?

04-28-13, 09:16 PM
My 2009 is all stock , and the boost gauge only goes about 1/2 way. Is that normal?

Stock boost is give or take 9 pounds on the unreliable stock gauge.