Turbo wastegate vacuum hose ....

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <34826592.B02A8BD2@poboxes.com> Gerard writes:

> Ever since I got this car (1990 200T) 4 months ago the
> hose running off the back of the wastegate to a solenoid (??) on the
> firewall has had a small bit of the string-braided covering that covers
> the rubber tubing, scuffed off. Yesterday I actually reached over to
> inspect it. The section missing the covering feels very soft and thin,
> while the rest of the hose feels good and solid.

Replace that hose and all of its friends.  
 
The 'solenoid' is the wastegate frequency valve.  You can make the ECU exercise 
it by putting a fuse in the fuseholder on top of the fuel pump relay and 
switching on the ignition.  Four seconds later the fuel pump will start running 
- pull the fuse and replace it.  Four seconds after you put it back, the 
wastegate frequency valve will start to tick - it may be almost silent and 
you'll have to hold it to feel it operating.

The ECU uses this valve to control boost when the WOT switch is engaged.  Small 
leaks don't matter because the ECU can compensate for them.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club