so its a 2.8 powered firebird. recently its been getting poor fuel mileage, took it to inspection and HCs and CO are through the roof so it failed emissions. I know that these indicate a rich condition. So, I know fuel pressure is about 42 psi, and it does have a rough idle/idle surge when the engine is warm. I think this rich condition is only occuring in closed loop as when the engine is cold it runs fine. I have 2 codes saying O2 sensor lean. So i'm thinking my sensor is wiped out, any suggestions before i make the change?

 

If you O2 sensor is not working right and it saying that your O2 is lean. Remember that your O2 sensor will not work while your car is in open loop while running. Your ECM will control the fuel until it goes into closed loop, then your O2 monitors your fuel ratio. Your ECM will keep adding fuel to get to the ideal 14.7 ratio. Change your O2 before you do anything else.