I was just curious. I understand how an O2 sensor works with a fuel injected car but how does the O2 sensor work on a carbeurated car? I thought what controlled the fuel was the air flowing through the carb and the adjustment screws. How can the O2 sensor make fuel adjustments and how does it know ? (without an ECU)

I have an '87 Accord (carb'ed) and it has an O2 sensor.

 

There is an ECU. The carb will have a jet with a valve controlled by the computer. It cycles like an injector to vary the fuel ratio. I'm not sure if the Honda one varies the fuel flow through the jet or the air before it picks up the fuel. Either way it acts like changing the jet or air valve sizes to vary the mixture. It is less precise and it's harder to get good drivability with good emissions, hence the death of the carb on modern cars.

 

An o2 sensor on a carb Honda, is used to increase or decrease air by activating and deactivating a mixture valve solenoid. So rather than taking fuel or adding fuel like in a Fuel injected system - I it adds more air or reduce air to control feul to air ratio. I hope that is answers your question.

 

I always thought an electronically controlled carb (like mine) had a sealed float bowl and the O2 controlled how much pressure was in the float bowl.

 

Thanks for the info . I was wondering how an O2 sensor would affect a carb. Do you think if I changed the O2 sensor, I might get beter gas mileage or would that be pretty pointless. The car has 241,000 miles ( and running strong).