A/F/R gauge for tuning

92b said

Can you explain this. If the charge is unburned then more oxygen is present in the exhaust. The sensor reads the presence of oxygen not unburned hydrocarbons. An HC meter could do that if you had a 4 gas analyzer hooked up.
When I see lean misfire on the dyno my o2 sensors show lean.

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A lean miss makes the O2 sensor read rich. there isn’t much left over oxygen but a ton of left over fuel.

So the O2 sensor says it rich and you pull fuel out and it gets richer until you kill parts.

Thats why the plugs and the O2 sensor have to match. So do the exhaust port.

Ironically, the exhaust port can lie to you too. The plug should be the ultimate arbiter of what the O2 sensor is telling you.