[s-cars] still looking for missing boost

[Mark Strangways]

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>
To: <s-car-list at audifans.com>
Sent: Monday, January 09, 2006 6:06 AM
Subject: [s-cars] still looking for missing boost


> 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
> 
> 
> 
> 
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