Why Do Used Cars Need New Catalytic Converters?
3 Answers
Some of the catalytic converters in used cars are no longer functional. Here is an introduction to catalytic converters: 1. Overview: The catalytic converter is the most important external purification device installed in a vehicle's exhaust system. It converts harmful gases such as CO, HC, and NOx emitted from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. When high-temperature exhaust gases pass through the purification device, the catalyst in the catalytic converter enhances the activity of CO, HC, and NOx, promoting specific oxidation-reduction chemical reactions. CO oxidizes at high temperatures into colorless, non-toxic carbon dioxide gas; HC compounds oxidize into water (H2O) and carbon dioxide; and NOx is reduced into nitrogen and oxygen. These three harmful gases are transformed into harmless ones, thereby purifying the vehicle's exhaust. 2. Performance Characteristics: Catalytic converters are stable in performance, reliable in quality, and have a long lifespan.
Having worked in car repair for over a decade, I've noticed that replacing catalytic converters in used cars is quite common. Mainly because old converters tend to fail after about seven or eight years of use, with their ceramic substrates prone to clogging or cracking. Last time, I saw a car owner whose fuel consumption suddenly skyrocketed, and black smoke was coming from the exhaust. Upon disassembly, the catalytic converter was completely clogged. With increasingly strict annual inspection regulations, failing emissions tests directly blocks the transfer process. Some inspection stations now use infrared detectors, and old converters with depleted platinum, palladium, and rhodium metals simply can't pass the test line. Actually, replacing it with a new one costs around two thousand including labor and parts, but it saves the hassle of frequent exhaust pipe repairs later on.
Over the years of working on used car refurbishment, I've found that catalytic converter lifespan is heavily influenced by driving habits. Cars that have used substandard gasoline are prone to lead poisoning in their catalytic converters, leading to permanent failure that can't be repaired. A common issue is when the front oxygen sensor fails and isn't replaced promptly, causing the air-fuel mixture to become imbalanced and ultimately burning out the catalytic converter. Nowadays, vehicles meeting China's National VI emission standards are even more sensitive—the system will immediately trigger a warning light and limit engine power if it detects excessive emissions. Last time I worked on an old Accord, the owner complained about poor acceleration. Scanning the data stream revealed abnormal voltage from the rear oxygen sensor, and upon removing the catalytic converter, we found its honeycomb structure completely collapsed. In such cases, the only option is a complete replacement—there are no alternatives.
