What Causes High Carbon Monoxide Levels in Cars?
2 Answers
Excessive carbon monoxide in car exhaust is generally caused by incomplete combustion in the engine. Since gasoline contains a large amount of carbon, it is normally oxidized into carbon dioxide during proper combustion. However, under oxygen-deficient conditions, it is oxidized into carbon monoxide. The reasons for incomplete combustion include the following: 1. Cold engine testing: At low temperatures, gasoline evaporation is poor, so the exhaust emissions differ significantly between a cold start and a fully warmed-up engine. National standards specify different exhaust emission indicators for these two conditions, and annual inspections measure the exhaust quality of a fully warmed-up engine. 2. Fuel injector leakage: If the fuel injector does not close tightly, gasoline may slowly seep out under pressure, leading to excessive fuel supply. Common causes include injector aging, carbon buildup, or impurities in the gasoline affecting the injector's closure. 3. Worn spark plugs: Aging spark plugs can reduce ignition energy, potentially failing to ignite the air-fuel mixture, thereby increasing the cylinder misfire rate. A misfire occurs when the spark plug fails to ignite the mixture during combustion, causing the unburned mixture to be expelled directly, resulting in failed emissions. 4. Faulty oxygen sensor: The oxygen sensor detects the oxygen content in the exhaust, and the ECU adjusts the air-fuel mixture concentration based on its signal. A malfunctioning oxygen sensor can cause the mixture to become too rich or too lean, affecting exhaust emissions. 5. Failed catalytic converter: Under high-temperature exhaust heating, the catalytic converter reaches very high temperatures, converting harmful substances in the exhaust into harmless compounds through oxidation-reduction reactions. A damaged catalytic converter will worsen exhaust emissions.
I've been in the auto repair business for over a decade, and high carbon monoxide levels are mostly caused by incomplete engine combustion. The most common issue is an imbalanced air-fuel ratio—meaning the proportion of air to fuel is off. If the oxygen sensor fails, the system can't automatically adjust the mixture, leading to unburned fuel and excess CO. A deteriorated or clogged catalytic converter is another major culprit. It’s supposed to convert CO into carbon dioxide and water vapor, but when it fails, emissions worsen. Everyday issues like dirty fuel injectors or worn spark plugs can also exacerbate the problem. High CO not only reduces engine power but also pollutes the environment and worsens air quality. To fix it, start by inspecting and replacing faulty sensors or catalytic converters, and clean the fuel system to maintain the proper ratio. Regular maintenance is key—don’t let small issues escalate.
