20v Boost Question

Henry A Harper III hah at alumni.rice.edu
Mon Jan 27 21:33:59 EST 2003

The 20v has a rather different engine management system and head, along
with possibly-different front brakes (the "UFOs") and suspension pieces
shared with the V8. Most other things are approximately the same, door
wires, door handles, seat heaters, DOT headlights, hydraulic system, etc.

See Scott Mockry's site for excellent troubleshooting info -
http://www.sjmautotechnik.com/20vboost.html - but an off-the-cuff free
diagnosis without pulling codes would be wastegate frequency valve failure
or multi-function (multi-failure) temperature switch gone bad, either of
which would limit boost to what is allowed by the wastegate spring alone,
1.4 bar. That's if it still runs fine apart from only showing 1.4 bar, if
there are driveability problems there might be some boost/vacuum leaks,
including bypass valve, or a dead mass-airflow sensor. 1.4 bar is
"limp-home" mode. Pull the codes and see what the ECU thinks is going on.

Henry Harper
http://www.henry-harper.com  hah at alumni.rice.edu
1991 200 quattro, 117k, only ever replaced an afterrun thermoswith on my
car as far as engine things go, diving into thermostat replacement tomorrow
1988 GTI 16v, 234k, really ought to get the idle switch cleaned up so I
don't have to bump the throttle to close it...

On Monday, January 27, 2003 8:32 PM, Steve Sherman
[SMTP:spsherm at attglobal.net] wrote:
> Hi.  This is my first post on the 20v list.  I've owned the 10v 86-88
> Avants for some years and am now looking for a 20v avant to replace one
> of these wagons.
> I've looked at a few, and have one or two in mind.  I am curious if
> there are any special things/problems that the 20v has that I might not
> be aware of from my 10v experience.
> And in particular, one of the 20v's I am looking at seems to ahve a
> problem boosting more than 1.4b (by the dash gauge).  Any thoughts on
> what that might be and quick ways to test.
> _______________________________________________
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