What are the causes of emission system failure?

[AlessandraRose]

The causes of emission system failure are: 1. Excessive spark plug gap; 2. The resistance value of the cylinder wire does not meet the requirements; 3. Failure of the oxygen sensor or carbon canister solenoid valve; 4. Excessive carbon deposits in the throttle or engine interior. The hazards of emission system failure are: 1. Excessive carbon deposits; 2. Affects the safety during vehicle operation and reduces the service life of the engine; 3. Causes sintering or detachment of the three-way catalytic converter carrier; 4. Excessive emission of harmful substances. The emission system is: The automobile exhaust system refers to the system that collects and discharges exhaust gases, generally consisting of the exhaust manifold, exhaust pipe, catalytic converter, exhaust temperature sensor, automobile muffler, and exhaust tailpipe.

[Shawn]

Last time my car's emission warning light came on and it really worried me. The mechanic said the most common cause is fuel quality issues—using low-quality gasoline that doesn't burn completely leads to excessive exhaust emissions. Another hidden reason is carbon buildup covering the oxygen sensor, which acts like the exhaust pipe's 'nose'; if it can't accurately detect exhaust concentration, the computer will wrongly report fault codes. Weak spark from aging spark plugs can also cause incomplete fuel combustion—my friend's car had its warning light go off by itself after changing the spark plugs. Oh, and a clogged catalytic converter is another major culprit, especially for cars that mostly drive in urban areas. I remember that repair cost me nearly two thousand yuan—the key is to always refuel at reputable gas stations.

[VonAngela]

After studying numerous emission fault cases, I found that many people overlook basic issues like intake pipe leaks. Last time my car threw a P0171 trouble code, it was due to aging intake manifold gasket leaks causing a lean fuel mixture that directly triggered the alarm. Another common mistake is a stuck charcoal canister purge valve - gasoline vapors escaping from the fuel tank can also disrupt the system. Actually, having the mechanic read freeze frame data with a diagnostic tool during maintenance is particularly useful; I often use this method to check intermittent faults. The most damaging thing is accidentally using leaded gasoline - just half a tank can destroy the catalytic converter, and the repair costs are painfully high.

[RebeccaLynn]

My car failed the exhaust emission test last year, and the experienced mechanic taught me a few key points to check: A ruptured diaphragm in the PCV valve can allow oil vapor to contaminate the exhaust system—if you hear a puffing sound when pulling out the dipstick, that's a telltale sign. Cold starts should produce water dripping from the exhaust pipe; if you see blue-white smoke, it usually indicates oil burning. Here's a money-saving tip—check the exhaust pipe temperature. A properly functioning catalytic converter should reach over 300°C. If the rear section feels ice-cold, it's likely clogged. In the end, I discovered the engine mount had sagged and crushed a vacuum line.