What are the reasons for excessive carbon monoxide in exhaust gases?
3 Answers
The reasons for excessive carbon monoxide in exhaust gases are: 1. Lean air-fuel mixture: Insufficient cylinder pressure, low engine temperature, leakage of air-fuel mixture from combustion chamber to crankshaft, fuel pipe leakage, damaged fuel pressure regulator; 2. Rich air-fuel mixture: Gasoline burns in an oxygen-deficient environment to produce oxygen. When the mixture is too rich, first check the choke valve opening and adjust the fuel needle; 3. Inaccurate ignition timing, intermittent ignition failure, faulty temperature sensor, leaking or clogged fuel injector, excessively high or low oil pressure, and other factors leading to high HC readings; 4. Uneven fuel injector atomization, resulting in unqualified air-fuel ratio and incomplete combustion.
I've been driving for twenty years and have encountered several instances of excessive CO emissions in the exhaust. Based on my experience, it's quite common. A dirty air filter blocking the intake passage, leading to insufficient oxygen and incomplete combustion, is the primary cause. Issues with the fuel system, such as leaking fuel injectors or excessive fuel pressure, can make the mixture too rich—too much fuel and too little air—causing CO levels to spike. A faulty oxygen sensor, which is supposed to monitor exhaust and adjust the mixture ratio, can send inaccurate signals, leading the engine control unit to make incorrect adjustments. Problems in the ignition system, like worn spark plugs or weak coils, can reduce ignition energy and slow down combustion. Additionally, emission system failures, such as exhaust leaks or a failing catalytic converter, can also lead to excessive CO. In short, poor driving habits or delayed maintenance often contribute to these issues. Regular cleaning or part replacements are recommended to keep your car running smoothly and environmentally friendly.
My beloved car was previously modified, but later it was detected that the exhaust CO levels exceeded the standard. After a thorough investigation, multiple factors were identified. The main cause is incomplete combustion: a clogged air filter is like a blocked nose that can't breathe, preventing the air-fuel mixture from leaning out; or poor fuel quality with excessive impurities leads to low combustion efficiency—an engine fed with dirty stuff will inevitably emit waste. If the oxygen sensor is covered with carbon deposits or has wiring issues causing it to fail, it can't provide accurate data to the ECU for adjusting the air-fuel ratio. On the ignition side, excessive spark plug gap or incorrect ignition timing allows some unburned fuel-air mixture to escape. System maintenance issues, such as a catalytic converter poisoned by sulfides or a stuck EGR valve, can also prevent emissions from meeting standards. Improper modifications, like mismatched high-power engine tuning, can exacerbate the problem. For safety, it's best to visit a 4S shop or a professional workshop for diagnosis, revert to factory settings, or upgrade the software to prevent recurrence.
