I have an 09 Cobalt SS,approx 9000 miles on ,always garaged,mint condition. Mods are GMS1,Hahn downpipe,K&N cold air intake. After GMS1 was installed by dealer car has always run great until recently. The car only goes out on nice days but has been maintained,that is oil changes and recalls done by dealer. Last week pulled it out to go get some gas and it just didn't sound right,after further investigation,it starts right up,runs smooth but when you go to push boost beyond 10 psi it just makes a lot of noise from the turbo and if you stay into it long enough will trip a cel,PO299 which is over/underboost. Have cleaned maf sensor,both 3 bar map sensors,upper and lower with maf cleaner,although they are clean it doesn't necessarily mean that they are good. Over the weekend I noticed that the lower charge pipe sensor boss on the pipe was never removed by the dealer,so I did it,no change. I disconnected my downpipe,thought possibly clogged cat,no change. smoke leak checked the entire charge piping system,showed up zero leaks.Tried disconnecting battery,wait 15 minutes then reconnect,no change. checked nuts on wastegate rod,fine. looked for broken or kinked lines,none that I can see easily but don't understand how it can purr like a kitten and run well until you get into higher boost levels. any thoughts

 

What kind of noise it is making? Maybe checking for shaft play although I don't think that's the problem

 

normally I would hear the psst between shifts which I don't seem to hear now. when I try to go into boost,it feels as if the car is laboring and a loud whoosing from the turbo. It also appears that on easy driving of the car the turbo is definelty noticeable with the whine of the turbo if you can understand that.

 

Stuck bpv maybe??

 

is there a quick way to test the bpv????

 

The bpv just take it out see if the diaphragm(rubber) is ripped/cracked

 

just came in from checking the bpv,appears to be fine,no rips tears actually very clean.

 

It could be the bpv solenoid then

 

there a quick way to bypass/check it or replacement only???

 

You can connect the bpv directly to the intake manifold see if that fixes the problem

 

well,came home and tried doing as you had suggested,took it out for a quick ride and runs like a bat outta hell again. I removed the hose from the BPV at the solenoid and it did have some vacuum but not like the intake when I pulled that hose.Should the BPV solenoid at that port have the same vac as the manifold because it def does not??????

 

anyone had to replace BPV solenoid and if so where did you get one or can I run all the time with manifold vac to BPV and plug that port on solenoid???thanks guys for the input........

 

I have a spare if you would like, I was hunting for a problem and the tb ended up needing replacement not the solenoid

 

Hey,waiting to hear from another guy that may have one as well,if that doesn't work out how much do you want for yours,I'm guessing from what happened to you with your TB, it was ordered and never used???Thanks

 

It's the one that was on my car originally got to lazy to go change it out again lol I got a few parts trying to fix the problem I installed the new aswell as a forge bpv trying to fix the problem the last thing I did was buy the tb and that fixed my problem but yeah they got for like 40+ shipping I could do like 20 shipped