dgkula

<center><img src="http://pictureposter.audiworld.com/102074/atw_vac.jpg"></center><p>So I'm getting tired of going into limp.

This week my local tuner pressure tested the intake side of the boost system with the traditional method - no leaks found.

Then they leak tested the vac side by spraying something (I think he siad break cleaner) on the hoses at idle - if it was sucked in he would hear the engine run rough. No leaks found.

ModifiedA4 suggested the PCV system; this would make sense as a leak in a check valve or PCV valve would not necessarily vent to atmosphere.

I managed to get mu hands on a home compressor (it works I topped off my tires) and plan to individually pressure test the check valves and PCV valve. So a few questions:

1. What is the spec on pressure held by the check valves. Will 30 PSI blow one of them? I want to be careful not to cause any damage.

2. The PCV valve (in the red box above) should shut when boost is applied from the manifold (through the suction jet pump) and not allow pressure to pass the T into the crankcase or the pancake valve? Can someone confirm?

Wish me luck.

ModifiedA4

and yes, you could put pressure into the line off the suction jet pump to test it.

i've personally actuated a new one using "human power", and I know it shuts under pressure and open under vac.

Also, your long term fuel trims obtained via vag-com predicted no vac or boost leaks.

dgkula

Any thoughts?

Tuner thinks that maybe the cat has coned and is restricting flow. That seems to make sense - but I've STFA and I haven't seen that scenario affect boost at high RPM but instead across the band. I get negative deviation at 5500 RPM.

Anyhow, I have to wait a month until I can get back in to see them (their schedule not mine) to unbolt the front of the cat and check it and the turbo from that side. Intake side of the turbo looks fine.

Where to look next?

ModifiedA4

verify the pcv system.