Need help with 200TQ Low Boost

["Southerlin, Russell S" <russell.s.southerlin@lmco.com>]

Quattro Heads,

Brother in laws 200TQ 20V isn't running too good.  I think I could take him
in my 87 5KTQ.

I am at a loss as to what to check now. Thought I would try the infinite
wisdom of the Q-List.

I am getting 1.4-1.5 bar max with hard 3rd gear (on the dash boost gage but
see below).

What I have checked: 
Vacuum hoses - All vacuum hoses appear O.K. although I have not removed the
breather hoses as Scott M. describes to check it.  I did specifically check
the WG F/V hose and the Bypass valve hose and they are O.K.

Air cleaner and exhaust - Air cleaner is clean.  I put a pressure gage on
the exhaust test pipe and saw no pressure on 3rd gear accel.  I thought this
was a little strange as Scott M. mentions there can be 2-4psi.  I blew into
the test pipe and it is not clogged.

WG F/V and Bypass valve - Replaced both with stock new units.  Boost appears
to have improved slightly (was getting 1.4 bar and now 1.5).  Intercooler to
intake (michelin man) hose is also new.  Output test are all O.K. WG F/V
does the clicking thing.

No trouble codes are stored (4444).  Was getting the idle switch code, took
the idle switch apart and touched up the solder joints and have not seen any
codes since clearing.

I teed in a pressure gage to manifold pressure and am getting 12 psi max
when dash gage reads 1.5 bar.  So the dash gage is correct for the altitude
([atmospheric 12psi + 12 psi boost] / 14.7 = 1.6 bar).

Engine sensors - I have checked (at the ECU connector) the idle switch and
pot. O.K., intake air temp., engine coolant temp. all are O.K.  Disconnected
the muti. Function sensor with no change in boost.

Here is the question: I pinched off the lower WG hose and test drove the
car.  I still only get 1.4-1.5 bar (Scott M. says this should give max.
boost).  Scott M. mentions this test but I do not see any causes if boost is
still low.  I think the WG F/V applies pressure to the bottom of the WG to
REDUCE boost??  So I teed in a pressure gage in the lower WG hose and sure
enough there is 0 psi with 3rd gear accel. And still 1.5 bar.  I do see the
pressure jump up to ~5psi when shifting gears and it flickers a little
~~1-2psi with light throttle when the boost initially come up.  BTW with the
WG F/V electrical connector disconnected I get little or no boost, it is
about 1.0 bar which sounds normal for this altitude. I applied oral suction
to the WG fittings (both upper and lower and it does appear that the
diaphram is O.K. i.e. it seems to hole a vacuum).  I took the WG top off and
inspected the diaphram it appears to be O.K. and the WG moves freely.


I do not see how the WG F/V can control boost if it applies pressure to
reduce the boost unless the WG spring is good for more than 1.8 bar (with no
boost pressure under it).

What do you think???

TIA
Russ
87 5KTQ (chip and S-Knobbben that runs better than BroInLaws 200TQ 20V)