[s-cars] still looking for missing boost

[Kenneth Keith]

Just put vacuum on the the nipple on the cap.  It should hold a vacuum
unless it is torn.

Ken

"Mark Strangways" <Strangconst at rogers.com>
>
> Sounds like the WG diaphragm is ripped.
>
> Next move I would make is to visually inspect the wastegate.
>
> Mark
> ----- Original Message -----
> From: "Theodore Chen" <tedebearp at yahoo.com>
>
> > symptoms: inconsistent low boost.  sometimes i get full boost or
> > close to it.  other times i get only a few psi (which i assume
> > is due to the wastegate spring).   it is inconsistent and changes
> > during the course of a drive.  it has occasionally even changed
> > during the same acceleration run.  sometimes it feels like it's
> > spooling slowly and then the boost suddenly comes on.
> >
> > things done so far:
> > 1.  replaced all of the little boost hoses between intake,
> > fuel pressure regulator, tee, moisture trap, and ECU.  used
> > bicycle pump to verify that it would hold at least 20 psi, and
> > a mityvac showed no leaks.
> > 2.  all hoses in intake tract (turbo to XC, XC to IC, IC
> > to TB) are samco with t-bolt clamps, and have been checked.
> > 3.  bypass valve is a forge, and its operation has been
> > verified with a mityvac.  i also tried to blow through it
> > to confirm that it wasn't leaking.
> > 4.  replaced little boost/vacuum hose from manifold to bypass
> > valve.
> > 5.  output tests run and WGFV (wastegate frequency valve)
> > clicks.
> > 6.  ECU checked with VAG-COM.  no codes except for engine
> > position sensor (the engine wasn't running so it's ok).
> > 7.  pressurized the hose from the WGFV to the WG to 20 psi
> > with a bicycle pump.  it leaked down quickly to about 10 psi,
> > held, and then suddenly leaked all the way down, with an
> > audible sound from the wastegate.  this happened every time.
> > i'm not sure if this is normal.  is it?
> >
> > can a WGFV pass the output test and still be bad?  is it
> > possible for the WGFV to fail intermittently?  or work well
> > enough to pass the output test but not cycle rapidly when
> > commanded to do so by the ECU?
> >
> > i'm not sure what to try next.  i could replace the O2 sensor,
> > since i'm not sure it has ever been replaced.  the car has
> > nearly 132k miles now.
> >
> > by the way, i now have a hoppen-sourced silicone turbo to XC
> > hose available if anybody needs to buy one.  perfect condition.
> > i wasted time swapping it, but at least i eliminated one more
> > possibility.
> >
> > -teddy