air fuel ratio going crazy whats wrong?
12-21-2005, 10:32 PM
#1
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air fuel ratio going crazy whats wrong? I just installed an a/f autometer gauge....i hooked it up to the purple wire on the O2.....when im at a constant speed the gauge suges all the way from the beg. of lean to almost rich really fast....when im at wot it stays constant at barely rich.....why is it going crazy at speeds besides wot? is my o2 bad? do i have a bad ground?
12-21-2005, 10:38 PM
#2
No and no...that's to be expected...you're AFR gauge is to monitor you 02 sensor obviously...Well your 02 sensor is kinda like a toggle switch...It tells the computer to give fuel on and then off, on and then off...At a VERY fast rate...It's just counting the oxygen molecules and then it is giving that table to the computer to tell it how much fuel to give it...the only way to get it to slow down and show an "accurate" representation is to use a wideband 02 and AFR gauge....
12-22-2005, 06:33 AM
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A wideband will only show stable readings at closed
loop, if it has the filtering / smoothing set pretty high.
It's the nature of the PCM's closed loop scheme to dither
the mixture and force frequent reswitching of the O2
sensor voltage across center. If you see a constant
value in closed loop it's only because somebody's
averaging the hash.
The narrowbands are as close to real time truth as
they can be (with only a small lag, as long as their
thermal needs are satisfied, and across a limited
range about stoich). The guage however has built
in assumptions about what voltage, away from center,
represents what AFR and those are fanciful at best.
Maybe you're swinging 10:1 - 20:1 at idle, or maybe
you aren't; 0.20 to 0.80V probably just swings across
6 LEDs because it was easy to design, not because
anybody had a real firm grip on combustion science
and sensor response. And the label goes on last. Dig?
Relax, watch the blinking lights, and try not to read
too much into it. Because unless it's a $50 sensor and
a $150+ package of electronics, it's making a big story
out of a little data.
loop, if it has the filtering / smoothing set pretty high.
It's the nature of the PCM's closed loop scheme to dither
the mixture and force frequent reswitching of the O2
sensor voltage across center. If you see a constant
value in closed loop it's only because somebody's
averaging the hash.
The narrowbands are as close to real time truth as
they can be (with only a small lag, as long as their
thermal needs are satisfied, and across a limited
range about stoich). The guage however has built
in assumptions about what voltage, away from center,
represents what AFR and those are fanciful at best.
Maybe you're swinging 10:1 - 20:1 at idle, or maybe
you aren't; 0.20 to 0.80V probably just swings across
6 LEDs because it was easy to design, not because
anybody had a real firm grip on combustion science
and sensor response. And the label goes on last. Dig?
Relax, watch the blinking lights, and try not to read
too much into it. Because unless it's a $50 sensor and
a $150+ package of electronics, it's making a big story
out of a little data.
