muncie21

iTrader: (14)

OK, so I understand that an O2 sensor detects oxygen and tells your car to +/- fuel to maintain stoic (~14.6).

My question is, how does a misfire affect an O2 sensor?
Does is see the additional unburned oxygen and think the bank is lean, thus increasing the fuel to that bank? OR?????

Brian68

Yes.

A rich exhaust has less oxygen since there is more fuel than the oxygen charge can convert.

As far as misfires go, technically the misfire is registered by the crankshaft sensor, not the O2 sensor, although the O2 reports the effect to the ECM.

edcmat-l1

iTrader: (10)

A single cylinder misfire makes a rough jagged saw toothed pattern in the O2. (Rapid downward spikes in voltage as the raw O2 passes) It happens too quickly for the fuel trims to react to it. It's not a rolling high low high low switching, which the fuel trims read and react to. The change in fuel trim % isn't significant because of the speed of the switching from the misfire.

I've got some scope screen shots somewhere of exactly what it looks like. If I can find them I'll post them.

jimmyblue

iTrader: (11)

If the misfire is persistent, though, its excess O2 would be part of the exhaust
stream average and begin to push trims.

Marky522

iTrader: (8)

And technically the 02 sensor reads lack of oxygen. Its a comparision to outside air, the greater the difference the more voltage is produced.

Mark