misfire/flat spot what caused it? too lean, or marginal ignition system/plugs well the thing will read rich bceause you didn't burn any of the charge and it will continue to read rich until you drive through the flat spot. it may or may not go lean after that .
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.
