What to Do If Exhaust Gas Test Shows Excessive CO Levels?
3 Answers
If the exhaust gas test shows excessive CO levels, you should check the air filter, spark plugs, intake air temperature sensor, and intake manifold pressure sensor. Additionally, add a dual-core friction-reducing repair agent and a high-efficiency cleaner. If these measures prove ineffective, clean the three-way catalytic converter. Below is some relevant information: 1. Excessive exhaust emissions mainly refer to carbon monoxide, nitrogen oxides, and nitrogen-hydrogen compounds exceeding the national exhaust emission standards. These excessive emissions are directly related to carbon deposits in the fuel supply system. More carbon deposits result in more severe emissions, while fewer deposits lead to milder issues. 2. Excessive carbon monoxide in a car's exhaust is primarily due to poor combustion. The main causes of this phenomenon include: failed spark plugs, poor ignition, excessive cylinder wall clearance, uncalibrated valve timing, a failed three-way catalytic converter, and poor fuel injector atomization.
The excessive CO level in the exhaust emission test is quite concerning, as carbon monoxide is harmful to health and affects the annual inspection pass rate. Common causes include incomplete engine combustion, such as a dirty air filter blocking the intake, leading to insufficient air and unburned gasoline, resulting in high CO levels; or aging spark plugs with weak ignition, causing incomplete combustion of the air-fuel mixture. I recommend starting with a DIY check—remove the air filter to see if it's clogged and try replacing it with a new one. If the spark plugs are heavily carbon-fouled, cleaning or replacing them might solve the issue. If these steps don’t help, visit a repair shop where they can use diagnostic tools to check the oxygen sensor or catalytic converter, as a faulty converter can directly cause CO levels to exceed the limit. Avoid sudden acceleration and prolonged idling while driving, as maintaining a stable engine speed can temporarily improve emissions. Don’t delay if the levels are exceeded—address the issue promptly to avoid long-term high emissions, wasted fuel, and unnecessary expenses.
Upon detecting excessive CO emissions, I immediately suspected an abnormal air-fuel mixture ratio, as excessive gasoline and insufficient air can cause this. The oxygen sensor monitors air quality; if it fails, the ECU's control becomes ineffective, leading to a spike in CO. A clogged air filter reducing intake volume is also a common culprit. I usually use an OBD tool to read fault codes and analyze the oxygen sensor's data stream—replacing the component if values are abnormal. The catalytic converter's core components degrade over time and require timely cleaning or replacement to prevent poisoning and failure. Fuel injector issues are another possibility; checking if fuel pressure is normal can help diagnose the problem. When emissions exceed limits, I recommend opening windows for ventilation during short trips to avoid CO buildup. After repairs, retest the exhaust values to ensure they return to normal. Such issues highlight engine efficiency—regular maintenance prevents minor problems from escalating, saving fuel and being eco-friendly.
