Bad oxygen sensor ?

[timsiford at hushmail.com]

First the standard O2 disclaimer....

Tuning by O2 voltages can be highly inaccurate.

With that said ... I would check two things...
1) Tape a Fuel Pressure guage to your windshield and have a buddy sit in 
the passenger seat as you do a WOT run.  Have him watch the FP guage ESPECIALLY 
in 3rd gear to see if your FP is decreasing.
2) Check your header collectors.  In some cases high speeds can act to force 
fresh air into the collectors if they are not tight.  The extra O2 will 
register on the O2 sensor.

Tim

At Wed, 8 Nov 2000 09:59:08 -0800, "Edmond" <euro at lvcm.com> wrote:

>
>
>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 :)
>
>