1990 200 missing/lean under boost

[Louis-Alain Richard]

NB means narrow-band o2 sensor, ie a standard O2 sensor. These are accurate
only near stoichometric mixture (14.7:1).In opposition to a wide-band O2
sensor that are used by engine tuners to correctly evaluate mixture under
load.

Brady, do you want to elaborate on that ? 

(shameless plug...) 
Brady Moffatt is an engine-tuner here in Montreal, owner of an urQ, a 4000Q
and a 200TQA.

Louis-Alain

> -----Message d'origine-----
> De : quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] De
> la part de David Michael
> Envoyé : 9 juin 2011 11:10
> À : David Yentema
> Cc : Quattro List
> Objet : Re: 1990 200 missing/lean under boost
> 
> 53 psi sounds right. Problem I had was that it randomly jumped to 55 psi.
> 
> I also replaced my dizzy because a bad Hall sensor was causing a mis-fire.
> But again, it was not boost related - it happened all the time.
> 
> Have you checked your valve cover gasket and injector o-rings - both
> common
> sources o vacuum leaks (which will cause you to set your base setting
> incorrectly)
> 
> Not sure what "NB" is but  at WOT, the system is running open loop, and
> the
> 02 duty cycle goes the a fixed number (can't remember what - maybe 68%).
> 
> A boost leak will usually result in black exhaust smoke ie - very rich
> 
> Dave
> 
> On Thu, Jun 9, 2011 at 10:49 AM, David Yentema <yentemad at rider.edu> wrote:
> 
> > These were the fuel pressures I got last time I checked:
> > cold control pressure 22psi
> > warm control pressure 53psi
> > system pressure 84psi
> >
> >
> >
> > On Thu, Jun 9, 2011 at 10:31 AM, David Michael
> <adavidmichael at gmail.com>wrote:
> >
> >> It's a long shot, but have you checked the control pressure? Moreover,
> if
> >> you can safely do so, you may want to figure out a way
> >> to monitor conbtrol pressure under boost.
> >> The control pressure is supposed to be very steady after the car warms
> up,
> >> but I had a control pressure regulatory go bad on me; it increased the
> >> pressure (leaned out the mixture) by a few PSI randomly. The failure
> was not
> >> related to boost, but if the control pressure is wrong, nothing will
> work
> >> properly. Remember, HIGHER pressure means LESS fuel....
> >>
> >> Dave
> >>
> >
> >
> >
> >
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