What to Do If Your Vehicle Fails the Exhaust Emission Test?
2 Answers
Solutions for a vehicle failing the exhaust emission test include: 1. Take the car to a professional repair shop for engine internal cleaning; 2. Use fuel additives and catalytic converter cleaners when refueling; 3. Replace spark plugs in a timely manner; 4. Clean the front oxygen sensor; 5. Switch to higher-quality gasoline; 6. Check the engine's working condition; 7. Increase throttle and drive several dozen kilometers on the highway. Reasons for failing the exhaust emission test are: 1. Poor fuel quality; 2. Faulty catalytic converter or oxygen sensor; 3. Large spark plug electrode gap; 4. Overly rich or lean air-fuel mixture; 5. Poor gasoline atomization; 6. Abnormal engine operation; 7. Dirty vehicle intake system, exhaust system, or fuel system; 8. Vehicle aging.
Last time during the annual inspection, my car failed the emissions test and I spent over 800 yuan to fix it. The main repairs included replacing four old spark plugs, cleaning the severely carbon-fouled fuel injectors, and also changing the air filter. The mechanic advised not to go for the cheapest gas all the time, as low-quality gasoline can easily clog the catalytic converter. After the repairs, I ran two tanks of fuel through it before retesting, and it passed. I suggest you first check the trouble codes to see if it's an oxygen sensor issue or an aging catalytic converter—treating the root cause saves money. Oh, and before the test, remember to drive on the highway for a while to heat up the exhaust pipe; testing with a cold engine is more likely to fail.
