Misfire! O2 sensor read lean or rich?


#1

Suppose misfire (eg, no spark) in one cylinder.
Will O2 sensor voltage read lean (≈0 mV) or rich (≈900 mV)?


#2

It will read lean because the dead cylinder pumps out air and unburned fuel.
The O2 sensor doesn’t measure hydrocarbons, only the oxygen in the air.