Oxygen sensor and high speed stumble

[Mark Romans]

Bob... get diacom.  Beg borrow or steal, maybe borrow a tech 1.  You can't
tune without them.  You can only guess.  Did it do this with the stock chip?
Without the above,  start with a fuel pressure gauge and check the pressure
at wot.  I have my fuel pressure set at 50 lbs at idle with the vacumn hose
disconnected and my block learn still goes up at idle to 135 or so.  When
driving on the highway it is below 128 a bit.  So...   I also have the stock
pump and a fresh filter.
Good luck.

Mark
-----Original Message-----
From: The Thibodeaus <vettenuts at efortress.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Thursday, October 29, 1998 4:12 PM
Subject: Oxygen sensor and high speed stumble


>I have an 90 Vette with a L-98 which above 4000 RPM loses performance and
>it has been suggested it is starving for fuel.  The fuel filter has 500
>miles on it.  I pumped some fuel out of the tank tonight after shaking the
>car to check for any sediment and the fuel looks fine.  I am running an
>adjustable fuel pressure regulator set at 48 psi.  I pulled the oxygen
>sensor tonight and it had some black soot on it indicating a rich
>condition.  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?  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
>