How to Pass Emissions

Three Methods: Learning the Emissions Standards, Getting an Inspection, Maintaining Your Vehicle
Emissions tests are commonly performed in some regions to try and reduce the carbon footprint of vehicles. Mandatory testing can be a frightening prospect for those of us who drive regularly. But learning the emissions standards in your area, how to schedule an inspection, and how to give yourself the best possibility of passing the test can take a lot of the stress out of the equation. If you have a vehicle of your own, see Step 1 to learn more about passing an emissions test.
Method 1 of 3: Learning the Emissions Standards
1. Check the emissions standards and procedures in your state. Many states require periodic emissions tests 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 don’t need to know the standards to have your vehicle tested. All you need to do is find a testing location in your area and schedule an appointment. They’ll tell you if your vehicle is up to the standards, and help you get it to code if it isn’t.
2. Find your particular vehicle group. An emission testing is different for different types of vehicles, and is required for a vehicle to be street-legal in some states, while in others there’s no requirement at all. Motorcycles are required to be tested in some areas, but not in others. Check with your local bureau of motor vehicles to make sure your vehicle needs to be tested. The most common exclusions are:
Vehicles manufactured pre-1975
Diesel vehicles manufactured pre-1997
Electric vehicles and hybrids
Trailers
2. Learn the common causes of emission issues. Failing the emission test is likely the result of some common performance issues in your vehicle. Learning to anticipate and correct these issues can help you pass the emissions test, once you’ve got it scheduled. The most common system failures are:
Out-of-spec fuel metering: This could be the result of the CPU, if your vehicle has one, or the fuel injection and carburetor unit.
Worn-out spark plugs: These can cause hydrocarbons to spike during the examination.
Vacuum leaks: These can occur because the MAP sensor is dysfunctional, or the hoses are faulty.
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.
Method 2 of 3: Getting an Inspection
1. Schedule a vehicle inspection. Get your car checked out by an emissions technician in your area to catch anything that you might have missed or overlooked. Typically, in states that require vehicles be emission-tested, these are as common as oil-change stations and Jiffy-Lubes. Look one up in your area and schedule a test.
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.
2. Make sure the check engine light is off before your appointment. If your check engine light is on, you will fail the emissions test automatically. If you don’t know what the problem is, an emissions repair shop can run a diagnostics test and fix the problem for you.
The car must be tested as-is, which means that even if the technician spots an issue that will obviously result in a failure of the test, the vehicle must be failed. If you know, for example, that you’ve got a leaky vacuum hose, or that your check engine light is on, you need to have those issues corrected at the shop or fix them yourself, before having the test performed.
3. 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 pressure for your catalytic converter, ensuring that you’ll get an accurate reading.
4. 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.
5. Pick a dry day for the test. Because a dynamometer will be involved in the test, driving on slippery roads in which you might lose some traction can affect the efficiency of your engine, possibly enough to skew the test. To give yourself the best possibility of passing with flying colors, schedule the test for a sunny day with nice weather and good driving conditions.
Method 3 of 3: Maintaining Your Vehicle
1. Change your engine oil regularly. If you haven’t changed your oil in over 5,000 miles (8,000 km), this is almost a necessity. If you have changed your oil in the past 5,000 miles (8,000 km), it may still be a good idea to get it changed again before having your car tested. Schedule an oil change, or do it yourself.
2. 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.
3. 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.
4. Adjust your carburetor for the proper air-fuel mixture. Running too rich can have a long-term affect on your engine’s ability to process hydrocarbons and CO emissions. It’s a good idea to periodically check how lean or rich your engine is running to make sure you’re within the proper specifications and keep your engine functioning properly.