What Causes the Buzzing Sound After Replacing the Three-Way Catalytic Converter?
2 Answers
Reasons for the exhaust pipe buzzing sound: Exhaust pipe aging: When a car is too old, the exhaust pipe is prone to aging issues, leading to loosening, detachment, or holes, which ultimately cause abnormal noise from the exhaust pipe. This situation is relatively simple to resolve—just re-secure or replace the exhaust pipe. Faulty three-way catalytic converter: If the car's three-way catalytic converter malfunctions, it cannot properly purify exhaust gases, causing them to clog and pressurize inside, resulting in abnormal noise from the exhaust pipe. This situation requires professional inspection and repair at a repair shop or 4S store. Faulty ignition system: If the car's ignition system malfunctions, fuel cannot burn normally in the cylinders, leading to symptoms such as weak acceleration, stalling, and abnormal noise from the exhaust pipe. In this case, a detailed inspection of the car's ignition system is necessary. Abnormal concentration of combustible mixed gas: If the concentration of mixed gas in the engine is too high or too low, it will cause abnormal combustion, resulting in abnormal noise from the exhaust pipe. This situation is more complex and requires professional inspection at a repair shop or 4S store. How to determine the condition of the three-way catalytic converter: Visual inspection. Check the exterior of the three-way catalytic converter for damage or marks. If there are scratches, cracks, etc., it is likely that the three-way catalytic converter has been damaged. If there are obvious gray spots in the center of the catalytic converter's protective cover, severe discoloration spots, or purple marks on the shell, the catalytic converter may have suffered from overheating issues. Check the engine's exhaust condition. Place your hand near the tailpipe outlet to feel the exhaust flow and check if the three-way catalytic converter is clogged or has poor exhaust flow. Another method is to open the air filter, remove the filter element, and observe if there is exhaust backflow during rapid acceleration, indicating poor engine exhaust flow. To check the condition of the TWC, also inspect if the secondary air injection pump is faulty. Use an infrared thermometer to judge. Compare the temperature difference before and after the TWC using an infrared thermometer. If the temperature difference between the inlet and outlet of the three-way catalytic converter is less than 10°C, the TWC is already damaged.
After replacing the catalytic converter last time, there's been a buzzing sound. I think it's mostly due to improper installation, like the exhaust connection not being tightened properly, causing airflow to escape and create the buzzing noise. It could also be a defect in the new catalytic converter itself, where the shape wasn't calibrated correctly during production, leading to increased vibration after installation. Once the exhaust system becomes loose, changes in engine RPM will cause resonance, amplifying the sound. I recommend checking all connection points for leaks immediately—use a cloth or soapy water on the joints; if bubbles form, there's a leak. Don't delay, as this could increase engine load, raise fuel consumption, or even cause a breakdown. Take it to a reliable repair shop to recheck all fastening bolts and gaskets, ensuring proper sealing. This should eliminate the buzzing sound—safety first, after all.
