AAN 101

[Jouko Haapanen]

So today I got my initiation in AAN diagnosis.  The patient - 1994 S4,
192 000km.  The patient lacked boost , ran poorly and misfired.  I was
told that the turbo was toast when I bought it.  So this morning I
pulled the intake boot off the turbo and lo and behold, the compressor
wheel spins freely and no excessive radial or axial play was felt my
my highly calibrated fingertips.  Off came the valve cover and I found
the proverbial fish tank in the plug recesses.  Dried it up, pulled
the plugs and and they looked like hell.  A quick look on my shelves -
no plugs of the correct type - a minutes drive down to Four Star
Motorsports where Dan Sprongl had plugs on the shelf.  Hey, it's going
to be nice living in Georgetown. Mike Hopton dropped in just as I was
leaving, what a small world.  Back to the shop, plugs in, Mike drops
in, clean up the ground points for the coil packs (thanks Mike) and
try it again.  Now it runs much smoother, still a definite misfire,
though, and still no power.    Mike and I somehow couldn't pull codes
at this point so I kept on poking.  A look underneath the car, pull
the accordion hose off the steel crossover pipe-IC intersection and
check it out.  Healthy.  Clean hose, hose back on.  Frustration
setting in, thinking of the coil packs - maybe a couple are dead?  Try
to pull codes again and out they come (thanks Scott for your helpful
site once again, code descriptions from your site):

2212
Throttle potentiometer,
short circuit to + or to ground,moisture or corrosion in harness
connector
Check throttle potentiometer resistance from idle to full throttle.
Symptom: Lack of power or boost pressure is not attained

2113
Hall sensor in distributor (3B, early AAN engines) or
camshaft position Hall Effect sensor on later AAN (S4/S6 engine).
Distributor alignment, faulty sender,
Mis-located sensor & distributor, Cam timing possibly incorrect on AAN
engine

Any ideas as to whether they could be related?  2212 seems fairly
straightforward, I'll poke around at that tomorrow.  It would help to
have that Bentley - all my VW and UrQ manuals aren't much help here.
What resistance range am I looking for on the throttle potentiometer?
How many connectors are there (car is at work - I'm back home now) and
which ones do I measure across?

2113 spooks me a bit.  Could I have a timing issue -belt that is off a
tooth?

The one nice thing about the UrS4 is that compared to the UrQ, there
is a ton of space to work underhod.  Still, it would help if instead
of engineering I'd studied to be a gynecologist.

Jouko Haapanen
Georgetown, ON