Three conditions must be met for a vehicle to meet exhaust emission standards: 1) the engine must be in good working condition, 2) the electronic control system must be functioning properly, and 3) the exhaust purification system must be working well. When detecting excessive emissions from a vehicle, the following items should be primarily inspected and adjusted:
1. Engine Adjustment
When the CO and HC readings are either too high or too low, it is essential to first rule out potential issues such as abnormal cylinder pressure, component phasing, or malfunctions in the ignition system. Then, adjust the carburetor's operating systems, particularly the idle adjustment. Subsequently, check the cylinder pressure; if it is significantly low, disassemble and inspect the cylinder head to check for valve burning, and whether the cylinder, piston, and piston rings are worn beyond limits. As these parts wear, they can cause difficulty in engine starting, incomplete combustion after rapid acceleration, and an increase in the content of compounds in the emissions.
When detecting low cylinder pressure, investigate the causes one by one and eliminate them. Assemble and replace parts according to technical specifications to ensure easy engine startup, sufficient power, and complete fuel combustion.
2. Clogged air filters and intake systems can lead to an imbalance in air-fuel mixture ratios. Therefore, it is essential to maintain air filters and replace the filter cores.
3. Proper Maintenance (Ignition System) Electrical Equipment
Ensure the breaker's platinum contact gap is normal.
Spark plug electrodes have the correct gap and are functioning well.
Precise ignition timing ensures a sufficient electrical spark to burn fuel completely. Appropriate delay in ignition can increase exhaust temperature, allowing hydrocarbons to burn off in the exhaust.
Ensure the normal and effective operation of the three-way catalytic converter.
The three-way catalytic converter is a crucial external purification device installed in the car exhaust system. It converts harmful gases such as carbon monoxide, hydrocarbons, and nitrogen oxides emitted from the tailpipe into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. Failing to clean and maintain the three-way catalytic converter in a timely manner can lead to a decrease in vehicle power, increased fuel consumption, and excessive emissions.
It is recommended to have the three-way catalytic converter cleaned without dismantling every 20,000 to 30,000 kilometers or once a year. After cleaning, the levels of carbon monoxide, hydrocarbons, and nitrogen oxides in the car exhaust are significantly reduced, with a particularly notable drop in nitrogen oxides; it improves fuel atomization and boosts combustion efficiency, thereby reducing fuel consumption by 5-20%; enhances cold-start capability at low temperatures and reduces noise; improves power performance, extends the service life of the engine and the three-way catalytic converter, ensuring regular maintenance of the vehicle. For catalytic converters that have exceeded their service life, timely replacement is necessary to ensure the normal operation of the vehicle's exhaust purification system.
6. Oxygen Sensor
Exceeding exhaust emissions doesn't necessarily indicate a problem with the three-way catalytic converter; a damaged oxygen sensor is also a significant and often overlooked cause. In engines equipped with three-way catalytic converters to reduce exhaust pollution, the oxygen sensor is an essential component. Once the air-fuel mixture ratio deviates from the theoretical air-fuel combustion ratio, the purification capacity of the three-way catalyst plummets. Therefore, oxygen sensors are installed in the exhaust pipes to detect the oxygen concentration in the exhaust and send feedback signals to the car's computer. The car's computer then adjusts the fuel injection amount to control the air-fuel mixture ratio near the theoretical value.
