What are the causes of abnormal car exhaust emissions?

[NoahAnn]

Abnormal car exhaust emissions can be caused by: 1. Aging of various car components; 2. Use of poor-quality fuel; 3. Failure of the catalytic converter. Methods to address abnormal car exhaust emissions include: 1. Inspecting the catalytic converter; 2. Using higher-quality fuel; 3. Replacing leaded gasoline with unleaded gasoline to reduce the emission of toxic substances in exhaust. The impacts of car exhaust emissions are: 1. Lead in the exhaust entering organs, disrupting acid-base balance and causing lead poisoning; 2. Carbon monoxide in the exhaust hindering blood absorption and oxygen delivery, harming the body and producing carcinogens; 3. Inhalable particulate matter irritating the eyes and lungs, increasing the risk of respiratory diseases.

[LaAlivia]

I was really scared when I saw blue smoke coming from the exhaust pipe during my last long-distance drive. It turned out to be worn piston rings causing oil to mix into the combustion chamber. Burning oil produces this kind of blue smoke. If you notice pungent white smoke, be cautious—it might indicate coolant leaking due to a cracked cylinder head gasket. This issue is common during cold starts in winter, but if it persists, it could be a serious problem. Owners of older cars should pay special attention to black smoke. Clogged fuel injectors or a dirty air filter can cause incomplete combustion of gasoline, leaving black carbon deposits on the inner walls of the exhaust pipe. Ignoring these issues can lead to failing the annual inspection. The mechanic told me the most troublesome problem is a failed catalytic converter—replacing that part can be really expensive.

[VanValentina]

Using the wrong gasoline octane rating can also cause exhaust issues. My friend's turbocharged car suffered from this. 92-octane fuel has poor anti-knock properties, making it prone to knocking and incomplete combustion, which leads to black carbon deposits from the exhaust pipe. A faulty oxygen sensor is particularly troublesome—when it fails, the ECU incorrectly adjusts the air-fuel mixture, causing fuel consumption to spike and emissions to exceed standards. Neglecting to replace worn spark plugs is also problematic; insufficient ignition energy results in partially burned gasoline being expelled, often leaving oily residue at the exhaust tip. Additionally, a stuck crankcase ventilation valve can suck engine oil vapor into the cylinders, burning it and causing HC emissions to exceed limits during inspections.

[McSimon]

Don't ignore pungent exhaust during inspection—it's likely a faulty ignition coil. I've handled similar cases; engines misfiring cause exhaust pipes to sputter with strong gasoline odor. EVAP system leaks are worse—a cracked charcoal canister line dumps fuel vapors directly into the exhaust. Turbocharged cars need extra caution—intercooler leaks disrupt air-fuel ratios, guaranteeing failed NOx emissions tests. Tuned cars are riskiest—incorrect AFR mapping can destroy catalytic converters within 20,000 km.