What Causes a Failed Emissions Test?

[Erick]

Here are the specific reasons for failing an emissions test: 1. Burning Oil: Worn oil rings fail to scrape off oil properly, allowing oil to flow into the combustion chamber, where it burns along with fuel. Alternatively, aging rubber seals on intake valves can cause oil to leak into the combustion chamber, resulting in oil burning. 2. Spark Plugs and Fuel Quality: Carbon buildup on spark plugs, dirty fuel injectors, improper air-fuel mixture ratios, or poor-quality fuel. 3. Electrical System Malfunction, High Carbon-Oxygen Content: Check for excessive resistance in high-voltage wires, overly large spark plug gaps, assess atomization and sealing conditions, and inspect whether the catalytic converter or oxygen sensor is malfunctioning, leading to non-compliant emission levels.