Why are catalytic converters removed from used cars?

[MadelineFitz]

Selling catalytic converters for profit. Below is an introduction to catalytic converters: 1. Introduction: The catalytic converter, installed in a vehicle's exhaust system as the most crucial external purification device, converts harmful gases like 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 this purification device, the catalyst inside the catalytic converter enhances the activity of CO, HC, and NOx, promoting specific oxidation-reduction chemical reactions. CO oxidizes into colorless, non-toxic carbon dioxide gas at high temperatures; HC compounds oxidize into water (H2O) and carbon dioxide; NOx reduces into nitrogen and oxygen. These three harmful gases are transformed into harmless substances, thereby purifying the vehicle's exhaust. 2. Performance characteristics: Catalytic converters feature stable performance, reliable quality, and long service life.

[HenryLynn]

I've researched this shady practice before, and it's primarily profit-driven. The three-way catalytic converter contains precious metals like platinum, palladium, and rhodium, and dismantling one can fetch thousands of yuan. Used car dealers lower purchase prices when buying vehicles, then remove and resell the converters for unethical profits. Some car owners are deceived into believing removal improves performance, when in reality it triggers warning lights and increases air pollution. Worse still, inspection stations now strictly monitor emissions, making it impossible for modified vehicles to pass annual inspections. When buying used cars, be alert if you spot welding marks on the exhaust pipes indicating modifications - it's best to test emission levels with professional equipment.

[FranciscoDella]

Honestly, the risks of removing this thing are way too high! I've seen some auto repair shops help people remove the catalytic converter to pass annual inspections, then install a dummy shell to fake it. But after removal, the exhaust is directly emitted, and the engine warning light on the dashboard immediately comes on. Computer diagnostics show the oxygen sensor data is completely messed up, and fuel consumption can skyrocket by two to three liters. Especially for China VI emission standard vehicles, the front section of the exhaust pipe is connected to multiple sensors—random removal might burn out the ECU board, costing over ten thousand yuan to fix. These cars also emit a strong rotten egg smell when driven, and even parking them in the garage is unbearable.

[DanielaLynn]

Veteran drivers know all the tricks in this trade. Some specifically target older Toyota and Honda models because their catalytic converters are larger and contain more precious metals. After removal, they weld in a cheap aftermarket replacement that costs only a few hundred bucks, leaving the next owner to deal with the consequences. The worst part is during cold winter temperatures—cars with stolen catalytic converters make a rattling noise from the exhaust pipe, like it's filled with gravel, because the internal ceramic substrate has been hollowed out. When buying a used car, you must crawl underneath to inspect the exhaust pipe welds. Factory welds are neat and uniform, done by robots, while aftermarket welds look messy, resembling centipede legs.

[DiCody]

The environmental protection department reported a typical case last year: a car dealer dismantled 137 catalytic converters in six months, profiting over 600,000 yuan. The three-way catalytic converter is like a car's kidneys; removing it causes carbon monoxide emissions to surge tenfold, killing roadside plants. Now, new three-way catalytic converters come with anti-theft brackets and engraved codes, but some still use angle grinders to forcibly remove them. When buying a used car, it's recommended to bring an OBD scanner to read the engine data stream, focusing on the air-fuel ratio and downstream oxygen sensor voltage values. Abnormal readings usually indicate tampering.