I pulled out the passenger side O2 sensor and it was covered in black soot. This is an obvious sign the right bank is running rich. The old saying if it’s running rich at the exhaust, it’s running lean at the motor.

There is some monitor sensor that is reading “lean” and commanding the closed loop to increase the fuel mixture.

These are the actual O2 sensors that I removed from the exhaust manifold. Only two sensors are being used, none at the output of the catalytic converter.

The right sensor (passenger side) is completely covered in black soot while the left side has the normal wear characteristics.

I found out that not all O2 sensors replacements are physically the same. Even though each may be 22mm or 7/8″ size, the body style of the nut and threads may differ. This makes a big difference when removing or installing the left side sensor (drivers-side).

Trying to gain access to the nut is damn near impossible without the use of a special O2 sensor removal tool with the extended length. See my other blog post for more information.