Hmmm. Thinking about it, unburnt fuel should show up as rich, no? So if it was an actual misfire, it would show as a rich spike? Or do I have that backwards??
Then again, less O2 from the lack of combustion.... Now I'm all backwards....
The oxygen sensor doesn't care about the fuel in the exhaust, it cares about the amount of oxygen in the exhaust (hence the name). A misfire will let more oxygen into the exhaust stream than a normal combustion cycle and the sensor will pick that up as a lean reading.
That's my thinking, I've seen this kind of behaviour when I was dealing with a miss at idle.
