I can't pass emissions. Limits are HC 220, CO 1.20. I read HC 318, CO 5.63. Timing is ok. O sensor 1 yr ago.
Car runs ok.
The reasons for the high emission are numerous. After awhile it goes away. If your car is not losing coolant, or if it does not puff white smoke while at normal operating temperatures, it is okay. The oxygen sensor is located in the exhaust system, either the exhaust manifold or the exhaust pipe very close to the manifold. They are very easy to change if done with the engine cold.