Emissions testing is commonly met with a loud groan by many car owners and auto enthusiasts. While taking your car for smog testing can feel like a hassle, it is an integral part of being a good citizen. Emissions testing your vehicle ensures that you are not releasing harmful chemicals into the environment around you as you drive. Unfortunately, failing an emissions test is never any fun. Not only does a failed test potentially prevent you from legally registering your car, but fixing the problem can sometimes be very costly. While there are an endless array of issues that can lead to a test failure, these are three of the most common.
Check Engine Light
Although it may seem unfair, an illuminated check engine light is a guaranteed failure in most states. Your vehicle's check engine light (sometimes known as a malfunction indicator light) is tied to your car's OBD-II system. Although this system monitors many sensors, its original purpose was to report data for emissions testing. When your OBD-II system detects a problem, it stores a trouble code in your car's computer and illuminates a warning light on your dash. A check engine light is often an automatic failure since many potential trouble codes indicate a problem with your emissions system.
Bad Catalytic Converter
The catalytic converter is a part of your car's exhaust system. Depending on the particular configuration of your vehicle's exhaust plumbing, you may have one or more catalytic converters. The purpose of this device is to convert harmful chemicals produced by the combustion process into a harmless gas. Specifically, nitrogen oxide (NOx) is converted into nitrogen and oxygen, while nitrogen monoxide is converted into the less harmful nitrogen dioxide. Emissions testing programs check for the presence of these gases in your exhaust stream, so a failing catalytic converter is all but guaranteed to cause you to fail the test even if you notice no other symptoms.
Too Much Fuel
Your engine relies on an exact ratio of air and fuel to burn cleanly and efficiently. When too much fuel is injected into your engine, your engine is in a "rich" condition. Carbon monoxide is produced in higher quantities when excess fuel is present in your engine, potentially overloading the ability of your catalytic converter to deal with the gas. Additionally, rich fuel conditions can result in greater-than-usual carbon dioxide output as a result of the normal operation of your catalytic converter. In either case, you are likely to fail your emissions tests. Unfortunately, rich fuel conditions can result from a wide variety of underlying causes, ranging from bad spark plugs to faulty O2 sensors.
Contact a local auto services provider to learn more about how you can fix these issues so you can pass your emissions test.