Overboost cutout on 5kcstq - datapoint

[Swann, Benjamin R. (BSWANN)]

A mechanic friend of mine just acquired an '87 5000 cs Turbo Quattro.

I had a problem that is common in these cars:  the engine would cutout under
hard acceleration.  Car is stock with no mods.

We hooked up a vac/boost guage teed to back of ECU.  It was hitting 14PSI of
boost and cutting out.

At my recommendation, he had already checked and replaced the lower and
upper wastgate hoses.

Suspecting the frequency valve we substituted a spare I had snagged from a
recycle yard.  A tad improvement, but this was not the cure.

Doing more tests with a mityvac, noted hoding no vacuem or pressure on
either side of the wastgate.

Verdict:  torn Wastegate diaphragm.

Ben
'85 4cskq x3 - silver, blue , white(parts) - wife is warming up to the blue
one.
'87 5kcstqw - had problem with lower wastegate hose when I purchased the
car.

p.s.Cheers to this list for I was able to lead a (newbie) AUDI tech to the
problem quickly having heard of the problem many times.