What are the solutions for failing emission tests?

[McAlivia]

The solutions for failing emission tests are: 1. Accurately determine the cause of exceeding the standard based on the steady-state simplified working condition test values of the exhaust. If the test value is above NO1000, the cause is catalytic converter poisoning. If the test value is NO2000, the cause is catalytic converter failure; 2. If the catalytic converter has failed, further determine whether it is reversible or irreversible failure; 3. Reversible catalytic converter failure can be resolved by using catalytic converter regeneration products for regeneration maintenance. If the vehicle has been driven for more than 100,000 kilometers, it is recommended to also perform catalytic converter cleaning maintenance; 4. Irreversible catalytic converter failure requires replacement of the catalytic converter, and it must be replaced with an original equipment manufacturer (OEM) part.

[StLiam]

I was really worried when my car failed the last emissions test due to excessive exhaust emissions. It turned out to be caused by severe carbon buildup on the oxygen sensor leading to an overly rich fuel mixture. The problem was solved after spending 300 yuan to replace the sensor. Older cars are also prone to incomplete combustion due to excessive spark plug gaps or aging ignition coils, which requires thorough troubleshooting. Pay special attention to the catalytic converter - I've seen a neighbor's car with a clogged converter from long-term use of low-quality fuel. Mechanics often recommend cleaning the fuel injectors and throttle body, but if carbon deposits are too severe, the entire exhaust system may need replacement. Before the annual inspection, remember to fill up with 95-octane gasoline and drive on the highway - the high temperatures can burn off some carbon deposits. If all else fails, you might have to pay a few hundred more to get it sorted through alternative channels. Failing emissions tests is a common issue with older vehicles, making regular maintenance absolutely crucial.

[LeAnastasia]

Failed emissions tests require identifying the root cause. From my experience, start by checking the air-fuel ratio. Air leaks in the engine intake system or MAF sensor malfunctions can affect combustion efficiency - last time my car failed due to aged intake manifold gaskets causing abnormal readings. Also pay attention to fuel quality; long-term use of gas from small stations tends to cause heavy carbon buildup, so I now exclusively refuel at Sinopec. The most overlooked issue is the EVAP system - when the charcoal canister saturates, fuel vapors leak. My car got stuck during last year's inspection because of this; we had to remove and purge it for two hours. Driving habits matter too - aggressive acceleration and frequent short trips with cold engines are particularly harmful. I recommend complete carbon cleaning every 20,000 km for optimal maintenance.

[LeTucker]

To address exhaust emission issues, I recommend a three-step approach: Start with basic checks by replacing the air filter and spark plugs, which can resolve 30% of common faults. For deep maintenance, clean the intake valve carbon deposits and the catalytic converter—my experience shows that using an intravenous cleaning method is more effective than disassembly cleaning. For core component inspection, use a diagnostic tool to read data from the oxygen sensor and EGR valve. I've seen cases where colleagues faced excessive emissions due to a stuck exhaust gas recirculation valve. Modified cars should be wary of potential sensor incompatibility. The most troublesome issue is catalytic converter failure—aftermarket parts have a short lifespan, while OEM parts are too expensive; it might be better to directly apply for scrapping the yellow-label vehicle to receive subsidies. New car owners should ensure fuel quality and periodically rev the engine to clear carbon deposits, which generally prevents problems.