Bad oxygen sensor ?

[Bruce Plecan]

Welllll,
I like to include a gear change.
The shift can be troublesome for knock on some stuff.
Bruce

Instead of using mph, maybe just use the G-Tech to measure G's between
4000-5500 rpm's in say 3rd gear.  Look for Max G's on the same section of
road
in the same direction.  Raise Fuel Pressure do test again, lower fuel
pressure do test again.  Go from there.
Mark
----- Original Message -----
From: Walter Sherwin
To: gmecm at diy-efi.org
Sent: Wednesday, November 08, 2000 7:17 PM
Subject: Re: Bad oxygen sensor ?


Wuuullll,  I for one would be genuinely interested in hearing what Bruce's
answer was at the 3rd GEN list (yeee gads, I can hardly find enough time for
just 2 lists, how does he do that?)..........

However, Edmund,  you mentioned in subsequent posts that you backed fuel out
via the VE tables and went from 98 to 104 MPH in the quarter!?  This seems a
bit odd after having just added headers.  At first glance I would have
suspected that your headers (and associated exhaust system) had actually
have forced you lean.  But, this would contradict your later findings.
Someone else suggested checking fuel pressure during the run (excellent
idea), but, this would not play well with reduce VE's either.  The list of
scenarios can go on, and on, and on, and each can be methodically eliminated
via real world testing, but, I want the Reader's Digest version
please........

What cal and ECM are you running, and is it MAP or MAF?

Walt.


I did several 1/4 mile runs after I installed my Edelbrock headers and brand
new o2 sensor. First and second gear are nice smooth 900mV range ramps. Once
it hits third gear is starts descending rapidly to about 400mV and stays
down until I let off the throtle. I wish I was at home so I can show you the
exact Diacom graph. I tried giving it more fuel (almost 95 in the VE tables)
between 90-100 KPA but it still does this. The engine runs fairly well at
WOT, but I cant really tune it w/out gettting some accurate info from the
sensor. My old 80K mile o2 sensor in the exhaust manifolds didnt do this at
all. Could this indicate a bad sensor ? I should mention at idle it goes
from 40-50 to 800-900 almost every 1/2 second. It does this at light cruise
too. Maybe it's time for a heated sensor ? Still downt explain the WOT
weirdness though since it should be nice and hot.



p.s. I know Bruce already answered this on the thirdgen.org message board,
but I wanted some more opinions :)

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