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Why Isn’t My Car Passing the Emissions Test?

Frustration. Even anger. These are emotions you might feel when your car fails its emissions test. You need it to pass in order to legally register your vehicle, and we get that here at SpringMasters Auto Repair. We can run a diagnostic test to find out why your car, truck, CUV, SUV, or van didn’t receive a passing grade when its emissions were checked. Here are common reasons that cause failures.

Dirty Oil

Get your oil changed before your emissions test. Dirty motor oil has more hydrocarbons, and these hydrocarbons can return a failed emissions rating. If you haven’t had your oil changed in 3,000 miles, this could be one reason why your car failed the test.

Fuel Mixture

If your fuel mixture is rich, i.e., there’s too much gas in it, your vehicle will fail an emissions test. The reason the mixture may be fuel-heavy is that you could have a problem with the fuel injectors or fuel pump, or your oxygen sensor might be bad.

Spark Plugs

The spark plugs are responsible for engine detonation, but if they are misfiring, they will increase the emissions coming out of your tailpipe. Spark plugs need to be replaced every 30,000 miles to, in some cases, every 100,000 miles. Get yours changed if they need it.

Gas Cap

It might seem odd that your gas cap can cause your vehicle to fail the emissions test, but it can. If the gas cap is loose, or if it cannot create a seal anymore and it is leaking, your vehicle will not pass the emissions test because there is gas evaporating from the tank.

Air Filter

The air filter in the engine should be changed every 12,000 miles. It’s a good idea to change your air filter before an emissions test, as well, especially if it hasn’t been changed in a year. If the air filter is clogged, there will be excess hydrocarbons in your vehicle’s exhaust.

Check Engine Light

Finally, if your check engine light is on, your vehicle will fail the emissions test no matter what. Even if the check engine light is on for no reason other than an electrical short, the emissions test will return a failing grade until such time as the check engine light turns off naturally.

Bring your vehicle into SpringMasters Auto Repair. We are located in both Chicago and Stickney, IL, and we’d be happy to find out why your vehicle failed its emissions test. Once we determine what the problem is, we can fix it.

Photo by welcomia via Canva Pro

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