Failing an emissions test is frustrating and troubling. Why did your vehicle fail the test? Can the problem be fixed? How much will it cost? Try not to panic too much. There are numerous things that cause a vehicle to fail; some of them are simple fixes and others might cost a pretty penny to repair. We here at DOC Auto can help. Here are five reasons why your vehicle failed its last emissions test.

Your Catalytic Converter Is Going Bad

If your catalytic converter is starting to go bad, your car, truck, or SUV will overheat and smell like sulfur. Another odor your nose might detect is rotten eggs. Many drivers report smelling them when their vehicle’s catalytic converter failed. The reason why a bad catalytic converter can cause your car to fail its emissions test is that it converts carbon monoxide into carbon dioxide.

Your Gas Cap Is Loose

Yes, we’re serious. Your gas cap actually plays a pretty important role in your vehicle’s fuel system. When it’s tight, it creates a vacuum seal, prevents fuel odors from escaping, and helps keep debris and dirt out of the tank. Your fuel system will return an error code to the main computer chip if the gas cap is too loose. In fact, your Check Engine light might even come on. If this is the reason your vehicle failed its emissions test it is an easy fix.

Your Mass Airflow Sensor Is Going Out

Your vehicle uses air as well as gasoline to start and run. Air and gas are mixed in the combustion chamber to create an accelerant for the spark plugs to ignite. The mass airflow sensor, or MAF as we like to call it, measures the air in your car, truck, or SUV’s engine. A failing MAF is unable to measure the air and regulate it. This might result in a lean mixture and emissions test failure.

Your Oxygen Sensor Is on the Fritz

Another important sensor in your automobile is the oxygen sensor. This measures the amount of unburned oxygen in your car, truck, or SUV’s exhaust. The exhaust mixture plays a crucial role in emissions testing. If the mixture is off, for example there is too much oxygen in the exhaust, your vehicle will fail the test. Oftentimes, replacing the sensor solves the problem.

Your Spark Plugs Are Worn

If your spark plugs are worn and cannot ignite the air/fuel mixture properly in the combustion chamber, your vehicle will struggle to start and run. This can lead to a rich air/fuel mixture because your vehicle is burning more gas to compensate for the power loss. Too much gas in the engine leaves too many dangerous emissions in your vehicle’s exhaust. Instant emissions test failure.

Stop by DOC Auto in Fredericksburg, VA, for an emission test. We have a shop on Chatham Heights (540-779-9814) and a shop on Courthouse Road (540-469-1773).