GM 3 wire O2 sensor dilemma

[Jon Fedock]

    I had the same thing happen to me. I had a 150 mV difference between
actual (tested at O2) O2 volts and reported O2 volts. Turned out to be main
ground wire to battery. This was on Turbo TA, so I was also concerned about
O2 accuracy - well as much as stock sensor can do. Use a DMM to check
voltage drop across grounds and remember a little is alot.
Jon Fedock
www.geocities.com/jonfedock


----- Original Message -----
From: <ECMnut at aol.com>
To: <gmecm at diy-efi.org>
Sent: Sunday, October 15, 2000 9:44 AM
Subject: GM 3 wire O2 sensor dilemma


> I'm having a wierd problem with the 02 voltage in my GMC Syclone.
> About 8 months ago, I noticed that the O2 numbers went from
> 950's to 8'40's... with no changes.  Fuel Pressure from my Walbro
> pump has been check several times under boost, and it's good.
>  I started making chips and adding fuel pressure
> to get the #s back up to where it has always run the best (950's),
> but by the time I got to 915, the black smoke from the rear of the truck
> convinced me I was *way* rich.  Now those numbers sound high,
> but I think Diacom does the wrong math with 02 calc, because I've
>  had readings as high as 1020 on the 02 in the past and general
> concensus for these trucks is mid 900's is the place to be..
> Besides I've owned this vehicle since new, and had a diacom as long,
> and know where it traditionally runs the best..  I recently installed
> a new AC/Delco 02 sensor, and it made no difference.   For
> some unknown reason, my 02 readings are down more than 100mv.
> I know that I could just say "screw it" and re-establish the 02 range
> where the timeslips are good, but when working with boost, fueling
> is not a good place to have a blind eye to the unexplained.
> Could this be a bad ECM or ground somewhere?
> Any ideas would be appreciated.
> Thanks,
> Mike V
> --------------------------------------------------------------------------
--
> To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
> in the body of a message (not the subject) to majordomo at lists.diy-efi.org
>

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org