What to Do If Your Vehicle Fails the Exhaust Emission Test?
2 Answers
If your vehicle fails the exhaust emission test, you can clean the three-way catalytic converter and oxygen sensor, clean or replace the spark plugs, and perform a deep engine cleaning. Here are detailed explanations of these three methods: 1. Clean the three-way catalytic converter and oxygen sensor: When a vehicle fails the emission test, the first things to consider are the three-way catalytic converter and the front oxygen sensor. Incomplete combustion of the engine's air-fuel mixture generates a large amount of carbon deposits, which are expelled through the exhaust pipe and adhere to the interior of the three-way catalytic converter and the surface of the oxygen sensor. Therefore, cleaning these components can resolve many emission-related issues. If the fuel used contains sulfur, lead, or phosphorus, it can poison the three-way catalytic converter, rendering it ineffective. In such cases, replacement is necessary. However, if the issue is solely due to carbon buildup, cleaning with an oxalic acid solution can restore its activity. 2. Clean or replace the spark plugs: Faults in the ignition system, such as issues with spark plugs or ignition coils, can also cause excessive emissions. Spark plugs are wear-prone components and are most likely to develop problems. Poor spark plug conditions can worsen emission pollution. Spark plugs are also prone to carbon buildup, which can be cleaned using sandpaper or cleaning agents to restore their activity, and the ignition gap can be adjusted. However, if the spark plugs are eroded or have reached the end of their lifespan, they should be replaced. Installing new or higher-performance spark plugs can significantly improve engine performance and reduce emissions. 3. Deep clean the engine: If cleaning the three-way catalytic converter and oxygen sensor and replacing the spark plugs still do not bring the emissions within the acceptable range, and assuming there are no faults with sensors like the air flow meter or temperature sensor, a thorough engine cleaning to remove carbon deposits is necessary. Cleaning components such as the throttle body, fuel lines, intake manifold, and fuel injectors can significantly improve engine performance. This will prevent the engine from operating under poor conditions that lead to incomplete combustion of the air-fuel mixture and exacerbate emission pollution.
My car failed the emissions test, so I did some troubleshooting myself. First, I checked the catalytic converter—it was probably clogged with carbon buildup. I took it off and cleaned it with a high-pressure air gun, then drove it for a few days before retesting. Surprisingly, it passed! I also learned that a faulty oxygen sensor can affect emissions, and replacing it only costs around a hundred bucks. For long-term maintenance, remember to drive at high speeds occasionally to clear carbon deposits or use fuel additives. Don’t procrastinate, or you might fail again next time—or worse, get fined if caught on the road. Start with simple fixes first, and if you can’t handle it, consult a professional mechanic before minor issues turn into major ones.
