Both the left and right catalytic converters have been replaced. There is a loud hot-rod type sound when I'm driving and the mechanic tells me the air sensor needs changing. The sound is stronger inside the car. Outside, it's more quiet. What is causing this?
Hello. It sounds like the catalytic converter gaskets may be causing a leak in the exhaust system. It is also possible that there is a leak or bad baffle in the muffler. This may be causing the hot-rod sound. It is not likely that the oxygen sensor is causing the sound that you are hearing unless there is an exhaust leak near the oxygen sensor. I would recommend that you take the car back to the place that replaced the catalytic converters so that they can check their work. If this is not the best option for you, then have a certified technician, like one from YourMechanic, complete an inspection of your exhaust system to pinpoint the problem.