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Mixture guage

I just installed one of those K&N fuel/air mixture guages and I think I
either have it hooked up wrong or something strange is going on. I hooked it
into the factory oxygen sensor on my 1980 Fiat Spider.

When the engine is cold, the guage reads 14.7 and stabalizes. I would think
that at first the guage would act erratic because the sensor is not hot and
it should later stabalize after it heats up but it acts just the opposite.

The guage has about 7 leds which ranges from something like 18.0 to 12.0.
During a lean condition none of the lights are suppose to function. During a
rich condition (12.0) all of the lights come on.

After the sensor is hot, the guage "bounces" back and forth like the lights
on an equalizer. It's almost a perfect rhythm. It's as if the sensor is
detecting an extreme lean condition then an extream rich condition, then
lean, then rich and so on.

Under acceleration, the guage starts to stabalize for a brief second. It
doesn't stay on long enough for me to tell exactly but I think it's around
13.5 .

Under deceleration, the lights go completely out for about a second or two.

I read the troublshooting section and it mentioned similiar conditions as I
mentioned above, but they are not the same thing. It mentions that one of
the lights (at the end of the band) may flicker because that light may be on
the brink of turning on. However it mentions nothing about all of the lights
flickering. Second it mentions the lights going out on acceleration (like
the engine is starving for fuel) but mine goes out on deceleration and
stabalizes on acceleration.

Seems like I read somewhere that if you test a "good" oxygen sensor with a
voltmeter it's suppose to fluctutate between 0.1 and 0.9 volts. This would
explain why the guage is constantly bouncing back and forth between lean and

Is this correct? I would think the fuel mixture should stabalize somewhere.

If the guage is reading correctly why does the mixture lean out when I take
my foot off the accelerator? It just happens for a second or two but still.
I imagine this may be normal because when the throttle plate closes the air
flow meter may still be in a different position for a brief second.


James Seabolt -----> mailto:jseabolt@domain.elided
ICQ # : 7344463

United States

1980 FIAT 2000 Spider (injected)
1981 FIAT X 1/9 (Injected)
1994 JEEP Wrangler (2.5l )
1976 Chevrolet Pickup (454 Big Block)

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