My car is having a problem maintaining 10psi in the upper revs (second turbo). It makes 10psi, and then skips back to 8, then back to 10, then back to 8.....
You get the picture. When it skips back to 8 psi(at full throttle mind you), it sounds like my blow off valve is releasing. I'm pretty sure that's what it is. My question is: If the blow off valve goes bad, it would be bad all the time, right? Also, is the blow off valve for the second turbo selenoid controlled?
Thoughts anyone?
James

 

"First Blow off valve" isn't controlled. I.E. it just plugs strait into the manifold.

The "Second Blow Off valve" (called the CRV, charge relief valve) is controlled by a solenoid. This is the first solenoid visible when you remove your pressure storage tank. It's the only one on the top of the solenoid rack.

The CRV solenoid is fed vacuum from the vacuum storage tank and pressure from the secondary turbo. It then feeds (one or the other) to the CRV ... per the electrical signal from the ECU.

Have a look at my my boost problem / diag.

Unless you want to pull your UIM and test each solenoid / hose, I would recommend that you start teeing into each suspect part and checking the vacuum pressure signal that it is receiving. I.E. the CRV, the "First blow off valve" ... I think that it called the ABV ... it's printed on the valve???

You could also remove the CRV and ABV and blow threw each with and without vacuum. Make sure that each one holds vacuum (on the control port) indefinitely ... I.E. doesn't leak.

Hope that this helps.