O2 sensor operation
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Senior User
Joined: Feb 2003
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From: Cleveland
O2 sensor operation
I hooked a scanner up to my 95 F-150. Gas mileage is about 15-16 mpg, less than what it used to be at 17+. I checked and replaced all the usual - plugs, wires, no brakes dragging, new cap and rotor, etc.
My scanner shows the O2 sensor varies dramatically as the engine runs at 1500-200 rpm. It ranges from 0.1 to 0.95 volts. Is this normal? Long term average is maybe 0.5 volts.
My scanner shows the O2 sensor varies dramatically as the engine runs at 1500-200 rpm. It ranges from 0.1 to 0.95 volts. Is this normal? Long term average is maybe 0.5 volts.
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Joined: Sep 2004
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.05 is lean voltage, .95 is extreme rich voltage.
.5 is an indication of 14.7:1 ratio.
What your describing sounds normal and here is why...
When your air/fuel is around 15:1 you get roughly .95 volts, when your air fuel ratio is roughly 14:1 you get roughly .05volts, .5 volts being in the middle or roughly 14.5 ~ 14.7.
Thats why they call it narrow band, you go from 14:1 @ .05 volts to 14.5:1~14.7:1 @ .5 volts to 15:1 @ .95 volts and theres the problem with the narrow band sensor, all the air/fuel ratios from 15:1 and richer will indicate a .95 and all air/fuel ratios from 14:1 and leaner will indicate .05, so as to how rich or lean you actually are, who knows?
Theres a graph in the link below thats used to describe this:
http://cherrypicker.tripod.com/id12.html
.5 is an indication of 14.7:1 ratio.
What your describing sounds normal and here is why...
When your air/fuel is around 15:1 you get roughly .95 volts, when your air fuel ratio is roughly 14:1 you get roughly .05volts, .5 volts being in the middle or roughly 14.5 ~ 14.7.
Thats why they call it narrow band, you go from 14:1 @ .05 volts to 14.5:1~14.7:1 @ .5 volts to 15:1 @ .95 volts and theres the problem with the narrow band sensor, all the air/fuel ratios from 15:1 and richer will indicate a .95 and all air/fuel ratios from 14:1 and leaner will indicate .05, so as to how rich or lean you actually are, who knows?
Theres a graph in the link below thats used to describe this:
http://cherrypicker.tripod.com/id12.html
Last edited by Motorhead351; Dec 16, 2005 at 07:09 PM.
