How to Deal with Unqualified HC in Vehicle Exhaust?
2 Answers
Replace with higher-grade gasoline, as higher-grade gasoline is cleaner. The content of harmful gases CO, NO, and HC after combustion is significantly reduced. You can refuel with higher-grade gasoline to purify the exhaust, making it easier to pass the annual inspection.
I often encounter this issue. Excessive HC values mainly depend on whether combustion is complete. Start with the simple checks: aging spark plugs can cause poor ignition, so it's recommended to try a new set; if the fuel injectors are clogged, the air-fuel mixture concentration will be off—they can be removed and cleaned with ultrasonic cleaning; a dirty air filter can also affect air intake, and replacing it only costs a few dozen bucks. Additionally, the oxygen sensor is particularly critical—if it malfunctions and gives inaccurate signals, the ECU will mess up the fuel mixture. Check if the connector is loose or directly measure the resistance value. By the way, the breather tube is most easily overlooked in older cars—a stuck crankcase ventilation valve can cause oil and gas to leak. It only takes a smoke break to unscrew and check. Finally, inspect the catalytic converter—open the exhaust pipe to see if the honeycomb structure is melted or clogged. If it's beyond repair, don't hesitate to replace it.
