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How to Pass Emissions

Three Methods:Learning the Emissions StandardsGetting an InspectionMaintaining Your VehicleCommunity Q&A


Method 1
Learning the Emissions Standards

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    Check the emissions standards and procedures in your state. Many states require periodic emissions tests to be performed to ensure that your car is running as clean as possible and not contributing to excessive air pollution. There are a lot of complicated numbers associated with the process that are probably not of interest to the average driver and vehicle owner, but you can research the Environmental Protection Agency standards for all vehicles here.
    • You can help avoid problems by keeping up on the maintenance of your engine fluids and filters. You should have your exhaust system checked periodically for any issues that may cause a future failure. If your check engine light comes on, have it serviced quickly to prevent further problems.
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    • Vehicles manufactured pre-1975
    • Diesel vehicles manufactured pre-1997
    • Electric vehicles and hybrids
    • Trailers[1]
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    • Worn-out spark plugs: These can cause hydrocarbons to spike during the examination. Just basic maintenance on the engine can sometimes cause emissions to spike.
    • Vacuum leaks: These can occur because the MAP sensor is dysfunctional, or the hoses are faulty. Your MAF sensor may also have issues with a vacuum leak and turn on the check engine light.
    • Air-injection and EVAP malfunction: If the air-injection system in the engine malfunctions, it won't be able to control the hydrocarbon and carbon monoxide emissions properly.[2] The EVAP system may be venting fuel vapors into the engine when it is not supposed to, causing high hydrocarbons.

Method 2
Getting an Inspection

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    • Just because your car is running fine and shows no signs of "problems" doesn't mean that it'll pass emissions. Many vehicles can continue operating well even though they've dipped under the local government regulations. This can happen when you don't keep up with scheduled maintenance.
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    Warm up your vehicle before testing. Drive your vehicle for at least 20 minutes before arriving at the emissions testing station. This will give your vehicle enough time to reach optimal temperatures for your coolant and oils as well as optimal temperature for your catalytic converter, ensuring that you'll get an accurate reading.
    • If you cannot drive your vehicle before the test then just run your engine in park or neutral at 1500 to 2000 RPM’s for at least five minutes to ensure your engine and exhaust are warmed up. In colder weather this may take a few minutes longer.
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    Keep your tires inflated properly. Proper tire pressure will put less strain on your car engine, which will improve your chances of passing the test. Equally-distributing the weight of the vehicle as it is driven during the test by the inspector will result in a higher likelihood that you'll pass. It's a good idea to fill up the tires to the proper specs before you take it in.
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Method 3
Maintaining Your Vehicle

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    Replace your filters regularly. Fuel and air filters need to be changed periodically to keep your engine as efficient as possible, and your emissions as low-impact as possible. Consult your owner's manual for specific guidelines regarding mileage, and keep a steady schedule of replacements. Check your air filter and, if it is dirty, change it before your emission test, since a dirty air filter can cause high hydrocarbons.
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    Use fuel additives if they're appropriate for your vehicle. Check your owner's manual to determine whether or not using Premium fuel is appropriate for your model. Other additives, like Clean Sky Clean Air can be added during refueling to purge carbon deposits from the engine during normal operations. Be aware that some additives could alter your emissions test and could be a cause of a failure. Be sure to tell your mechanic what additives you are using if you have failed. The additive could have been the cause.
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Community Q&A

Add New Question
  • Why might my car fail the NOX test?
    wikiHow Contributor
    You could have a bad catalytic converter, an issue with your exhaust gas recirculation system (EGR), or a lean fuel mixture, to name only a few possibilities.
  • Can I pass inspection without a catalytic converter?
    wikiHow Contributor
    No. If your car came with an original catalytic converter, it must have one to pass inspection. They will look for it.
  • Do I have to get an oil change before an emissions test?
    wikiHow Contributor
    If it's been under 4000 miles, no, but everything clean leads to a better test. Replace your PVC valves and air filters if you have not done so in the last 12000 miles.
  • If I fail my test, can I still get a license plate sticker?
    wikiHow Contributor
    No, an emissions certificate that shows your vehicle passed emission testing must be provided to your local DMV to acquire a new registration sticker.
  • Is an emissions test the same as a smog check?
    wikiHow Contributor
    Yes, they are the same, although different states' testing protocols look more closely for different pollutants.
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  • Scheduled maintenance is a guideline and servicing may need to be done more often than the recommended service intervals. Even if you State does not require a vehicle inspection keeping up on repairs and maintenance will benefit for a better running vehicle that gets better fuel mileage with less breakdowns.
  • Use additives in your fuel to help reduce emission levels. Additives are typically poured into the gas tank while refueling at a station. They help to clean out your vehicle's internal system, allowing for more efficient usage of fuel and improving overall engine performance.

Article Info

Categories: Car Maintenance and Repair

In other languages:

Español: pasar la prueba de emisiones de tu auto, Русский: пройти тест на выброс в атмосферу, Português: Passar em um Teste de Emissão, Italiano: Superare il Test sulle Emissioni del tuo Veicolo, Français: réussir un test d'émissions, Bahasa Indonesia: Lulus Uji Emisi, Tiếng Việt: Vượt qua Bài kiểm tra Phát thải

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