RE: Audi 5000 Fuel Distributor

[steveb@falcon.kla-tencor.com (Steven Buchholz)]

 # I developed the exact same symptoms last week with my '88 5kcsqw.
 # Figuring it was either the fuel distributor valve or a fouled injector,
 # I ran two tanks with injector cleaner added to see if I might get lucky
 # and avoid replacement of the offending part.  After about 200 miles, the
 # problem had diminished to nothing.  This chilly morning, a few days
 # later, a slight miss returned - but disappeared again as the car warmed
 # up.
 # 
 # I suspect I've got an injector that was sticking in the closed position.
 # I am leaning toward this as an explanation, because the engine felt more
 # like there was a distinct cylinder miss than a more general lean state
 # from a sticky distributor valve.  We'll see how it does after a few
 # months...  maybe a good cleaning will manage the problem.

... you really need to be careful not to be "penny wise and pound foolish" 
when you do things like this.  If you have a cylinder that is running lean 
due to a malfunction of the FD or injector your EGT can get much higher 
than nominal.  This may result in burned valves if it goes on for too long.  
I suppose that if the injector were completely plugged you wouldn't have a 
problem as you'd simply be pumping air ...

I'd recommend that anyone that thinks they have an injector problem pull 
the injectors and check the spray patterns rather than running a bottle 
of Techron and crossing your fingers.  It really isn't that difficult to 
pull the injectors out to check them ... and that would also give you a 
chance to see what shape the seals are in ...

... to the original poster ... if you have a problem that develops as the 
engine warms up it may in fact be due to the ECU trying to lean out the 
mixture when it goes closed loop.  Too bad the car doesn't have an EGR 
valve ... the symptoms fit pretty closely to that.  :)  Here I'd recommend 
that you get a fuel pressure gauge and a duty cycle meter and check system 
and control pressure as well as the "OXS duty cycle."  Another possibility 
you might want to look for is an intermittent vacuum leak ... and the can-
didate I'm thinking about is that stupid hose that runs up the spark plug 
side of the engine and connects the crankcase to the "PCV" system.  I cur-
rently have that silly thing covered with duct tape on the '88 5kCSQW ...

HTH!
Steve Buchholz
San Jose, CA (USA)