Vacuum issues?

[BeardedFool]

Okay... Turbo bypass valve connected to plastic tube but not the aluminum one... Car idles around 1300 to 1400 rpm. If I put my hand over the end of the aluminum tube, idle shoots up to 1500 rpm. When I remove my hand, the rpm drops to 900ish and then back to 1300ish. I can feel a vacuum affect on that tube. If I blow into it, the car stalls and if I cap off the other end of the bypass valve so that the only air getting to the intake manifold is what goes through the filter, MAF, turbo, intercooler, then to intake manifold, the car stalls.

[GeoffR]

Okay... Turbo bypass valve connected to plastic tube but not the aluminum one... Car idles around 1300 to 1400 rpm. If I put my hand over the end of the aluminum tube, idle shoots up to 1500 rpm. When I remove my hand, the rpm drops to 900ish and then back to 1300ish. I can feel a vacuum affect on that tube. If I blow into it, the car stalls and if I cap off the other end of the bypass valve so that the only air getting to the intake manifold is what goes through the filter, MAF, turbo, intercooler, then to intake manifold, the car stalls.

The bypass valve is required to allow air to bypass the compressor, at idle the bypass is open. It is possible that the turbo is producing more air than required and thus the mixture is too lean without dumping some.

I would replace the bypass valve.

Also check for any fault codes related to the fuel system.

[BeardedFool]

Sadly, I have replaced the bypass valve with absolutely no change from old to new valve.
I have thrown in the towel for the time being and have an appointment with one of my local "Saab specialists" to let him diagnose it in a week and a half. Meanwhile, I'll be working on the cosmetic issues to get it cleaned up and solid.

[BeardedFool]

Turns out that I must have missed a vac hose. I did replace everyone that shows up in the schematics and other postings about vac lines... but I missed one. Mechanic said it was a short one on the back side of the engine.