RJ_RS_SS_350

P2261, that sounds more like your description. When you said "fluttering when releasing pressure" I thought that sounds like bypass valve. So it's probably either the valve itself, or the bypass solenoid that I mentioned before, or hoses or wires associated with it.

You still may have a problem with the boost control solenoid also, but fix the P2261 first and see if you still overboost.

RJ_RS_SS_350

My post #40 in the thread that donbrew linked to has a couple options for a new bypass solenoid. You can use the search window above to find how to replace the valve, either OEM or a unit by Forge, it's all pretty easy to do.

SHAGGYMEOW

I replaced the bypass valve on the side of the turbo with the one from forge i'm still getting 30 pounds of boost when I should only be getting 15 started getting that 2261 code and it 234 code is it possible the wastegate is not sealing correctly and if so where can I get a aftermarket one because Chevy wants 421 for a new wastegate and turbo ?

RJ_RS_SS_350

Hmmm.... P0234 points to the boost control solenoid, P2261 points to the bypass... I wonder if it could be a ECM problem. Or else they both are bad. So you either take it to a shop to diagnose(i.e., test the solenoids and ECM), or throw parts at it($40+ for bypass solenoid, $70+ for boost control).

It's unlikely that it's the wastegate itself. P0234 is usually the solenoid, sometimes the wire connector, rarely leaky hoses. There is a diaphragm that the solenoid operates, which in turn moves the wastegate, your mechanic could test that also. I'm not sure if it operates off vacuum or pressure, but the way it's oriented, I would guess boost pressure pushes on the diaphragm, opening the wastegate when needed. In all my research on P0234, I cannot recall any reports of a bad wastegate or diaphragm.

RJ_RS_SS_350

Researching the P2261, it looks like the bypass valve could be stuck. I seem to recall someone saying the Forge units may need lubrication, or maybe the spring is too strong. I don't know if you checked the vacuum tank for leaks, but this thread says you should:https://www.chevyhhr.net/forums/2-0l...t-36554/page3/

SHAGGYMEOW

So I replaced the bypass valve with the one from forge and drove the dtcs are cleared but I'm still overboosting and the boost is not that strong but it still goes to 30 should only be 15 I checked for codes nothing was gonna try to see if the waste gate is misajusted or maybe the nuts backed off when I go to the shop tomorrow but last time I was under there the nuts looks tight and they have never been ajusted/ or touched. If that's good then I was thinking maybe the bypass solenoid but wouldn't I have codes ????? Any ideas

Oldblue

I live by a code, the Code of the West!! Geological not Kanye!!!

RJ_RS_SS_350

Even if the wastegate had been adjusted at some time, the ECM relearns back down to 260 ft lbs of torque.

I seem to remember something about people putting a "pill" in some line, but I thought that was a short term gain also, being relearned back down. You might search over at cobaltss.net ,that's where I saw it.

Not likely to be the bypass solenoid, more likely to be the boost control solenoid, but you really should be getting codes by now.

If you are in overboost condition for 3 seconds continuous or 50 seconds cumulative, the turbo will cut out to protect the engine. Is this happening?

I'm a little confused: you say the boost is not that strong but goes to 30. What do you mean?

You also said on April 28 that you replaced the bypass valve. Now you've replaced it again?

SHAGGYMEOW

No I only replaced it once but I was giving it some time to drive and what I mean by that is when I Floor it going to boost it'll run up to 25-30 you hear the turbo spool but it's only for a couple seconds and then it drops back into vacuum its kind of like a limp mode but there are no codes

firemangeorge

There should be(probably is) a code or codes present. Are you sure your OBD port connection is good ? Or try another code reader.