01 Honda Accord cylinder misfire, running rough?

[mechtech2]

A bad cat is identified by the rear O2 sensor .
It should read differently than the front O2 sensor. The front reads the mixture, the rear what comes out of the cat. If they are the same, the sensor or the cat is bad.

 

[steven88]

so it should throw a code when the cat goes bad?

 

[Market525]

Yes, it will throw a code. P0420 if my memory serves correctly. Cat efficiency below threshold -- or similar- is what the message will be.

 

[mechtech2]

Sometimes cats or O2s have to be pretty bad before a code is thrown.

 

[CourierDriver]

o the days of points plugs rotorbutton and a condenser and I still got 30mpg on that old car