Supafly94

my 09 SS has turbo underboost, does anybody no of any turbo specialists in the phoenix area, preferably in the east valley?

DrLoch

Check the intercooler for cracks

donbrew

Or, find out what codes are causing the CEL. That would narrow the places to look.

I ask because I know it is on without you mentioning it.

ACLR8R

What are the codes?

Oldblue

When you connect an OBD II reader to that connection under the dash, most parts palaces will read it for free, the light might not be lit but there could be a stored code.
AutoZone or O'Reilly's
Ask for the code print out and post the code for example P0010.

Supafly94

the code is no longer showing, oreillys said they couldnt look at old codes. I remember when it came up they said it was turbo underboost? I just dont think it is working correctly , if you watch the boost gauge it spools up than just kind of falls on its face?

RJ_RS_SS_350

How high does the boost go before it falls flat?
Do you have to restart the car before it will boost again?
Is the car stock or tuned?

The suspects are: (in no particular order)
Boost leak/vacuum leak
Bad diaphragm in the bypass valve
Bad bypass solenoid
Depending on your answers to above, maybe Bad boost control solenoid

Have you tried to read codes? 'Stored' does not necessarily mean 'old', there could be a pending code that has not yet illuminated the CEL. And make sure you don't disconnect the battery or clear any codes yet.

Supafly94

I get about 15-20 boost, I bought the car used so I dont know if its tuned and I dont have to restart the car. If i keep accelerating hard it actually feels like the power is surging, and I have started to notice a whine when the turbo is boosting.

RJ_RS_SS_350

Let's hope the whine isn't a lubrication issue. Make sure the engine oil level is good, as the turbo is lubricated by the engine oil. It is also cooled by the coolant, so make sure your coolant is in good shape.

Green coolant(which I hope you don't use here) has a service life of a year or 2. The proper coolant, DexCool, has a service life of up to 5 years. If the engine has overheated, the DexCool needs to be replaced.

Still no codes? P0234 would be an indication of overboosting. 15-20 PSI on a stock tune would be an overboost. An overboost of 3 seconds consecutive or 50 seconds cumulative will set the code, and the turbo will be limited to just 1-3 PSI. Upon restarting, the turbo will boost again. Sounds like this is not the case here.

Here is a post to help you determine if you have the GM turbo upgrade(GMTU).
https://www.chevyhhr.net/forums/ss-s...64/#post766048