Oxygen sensor and high speed stumble UPDATE

[Zack]

>  Here is my question, by upping the fuel rail pressure to 48 psi
>am I starving the engine at high RPM because the pump can't flow 
> enough fuel at that pressure?  Does this seem logical? 


Yes and no.  If you ECU doesn't have a self-learn mode, since the 
regulator acts on the return line and will simply shut off return 
flow if the pump can't maintain pressure, the worst that can happen 
in that case is upping the regulator setting would have no effect (if 
you were at worst case where the pump could not even maintain 
pressure at the lower regulator setting).
	However, if the ECU has a self learn mode, which calibrates injector 
pulse width to O2 sensor reading during closed loop, then upping the 
fuel pressure to a level that cannot be sustained at WOT -can- lead 
to a worsening of the leaning out condition.  The ECU will learn 
that it needs to decrease injector pulsewidth by some certain 
percentage to deliver X amount of fuel during closed loop, and it 
will continue to apply the same factor during open loop as well.  
Since the correction is based on fuel pressure, if the pump can't 
maintain the same fuel pressure under WOT that it does during cruise, 
this  scaling back of injector pulse width by the ECU will worsen the 
leaning out at WOT.
	Having said that, this doesn't sound like that's your problem, 
because a reading of mid-900's on the O2 sensor indicates a very rich 
mixture, 850-900 mV is the area most people I've talked to shoot for 
when tuning.  Does the pinging problem originating from a particular 
cylinder(s), or are they all pinging?  Just curious whether one 
cylinder might be getting inadequate fuel delivery for some 
reason, which you're not seeing on the sensor because of the overall 
rich condition.  	

Z

 I increased the 
pressure
>compensate for a ported plenum and also to overcome a pinging 
problem
> >(several prior posts made to this board and Vettenet on this nightmare) but
> >it hasn't worked.  I am working with the chip programmer to resolve some of
> >the pinging problems because I have found that they completely shut of the
> >EGR function.  So, should I lower my pressure?  Any suggested value?
> >Thanks for any suggestions.
> >
> >Bob T
> >
> Today I ran the car up in second gear with a fuel pressure gage taped to
> the winsheild.  The pressure never really dropped below 40 psi so it looks
> as though the fuel pump is OK.  The knock sensor pulled out about 4 degrees
> of advance maximum.  The oxygen sensor was reading about the mid 900 level
> millivolts at WOT.  The maximum advance at WOT was 29 degrees.  One thing I
> did notice though was that the Auto X-Ray never indicated open loop at WOT
> even though my integrator and block learn were at exactly 128 which
> indicates that it was not using these parameters.  Any comments are
> welcome.  I don't have a correlation of oxygen sensor voltage to AF ratio,
> am I too rich?
> 
> Thanks
> 
> Bob T
>