Reasons Why Your Car Might Fail An Emissions Test

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Marietta, GA, residents know their vehicles have to pass emissions tests. In fact, we’re required to have our vehicles tested each year. MMW Repair not only conducts emissions testing we also repair vehicles that fail the tests. What are the primary reasons why a car, truck or SUV might fail an emissions test? Here are the most common repairs we make to ensure the vehicle passes the retest.

Fuel/Oxygen Mixture

Your vehicle is equipped with an oxygen sensor that gauges the air/fuel mixture in your exhaust. If your fuel injectors aren’t functioning properly or your oxygen sensor is on the fritz, your vehicle might not pass an emissions test because the air/fuel mixture is too rich. Your fuel injectors could be pushing too much fuel through your exhaust system which can, if left unrepaired, damage your catalytic converter.

Worn Spark Plugs

Worn spark plugs can also increase gas emissions. Today’s engine oftentimes doesn’t need its spark plugs changed until the 100,000-mile milestone, but if you’ve noticed your car misfiring, lurching or stalling, it might be time to have the plugs inspected. While inspecting the plugs, we’ll also check the plug wires and ignition coil to make sure everything is working properly.

EVAP Defects

EVAP stands for Evaporative Emission Control System and when it isn’t working as it should be, gas vapor can escape the tank, which is definitely an emissions failure. Generally, if your vehicle fails a smog test due to an EVAP issue, the issue is a leaking hose or vent. Another cause of gas vapor leaks is a loose gas cap that no longer seals when tightened. This is common in older cars.

Air Filter

Here’s hoping this is the reason why your vehicle fails an emissions check because replacing the air filter is quick and easy. If the air filter is old and dirty, it traps hydrocarbons, which is one element tested for in an emissions test. An air filter should be changed every 15,000 to 30,000 miles, but check your owner’s manual to see what your vehicle’s manufacturer recommends.

Catalytic Converter

Finally, as we mentioned above, a rich air/fuel mixture can damage your catalytic converter and a malfunctioning one will definitely return a failed emissions test. The catalytic converter’s job is to convert harmful gases into environmentally-friendly ones before they are expelled in your vehicle’s exhaust. Functional catalytic converters are crucial to passing an emissions check.

MMW Repair is a full-service emissions testing station in Marietta, GA, and we’d be happy to give your vehicle the once-over prior to your smog check. Call us today at 770-214-4688 to set up an appointment.

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