brake discIn Connecticut, drivers are required to have an emissions test done on their vehicle every two years. The results are sent to the Department of Motor Vehicles (DMV). Certain states require annual tests or roll them into an inspection that further assesses the vehicle’s safety. Emissions tests measure the pollutants your car’s exhaust system produces, with the goal of reducing the amount that ends up in the atmosphere to reduce smog.

OBD Check vs. I/M240 Test

States require either an onboard diagnostic (OBD) check, which is done on vehicles manufactured from 1996 to the present, or an I/M240 dynamometer test for vehicles manufactured between 1981 and 1995. During an OBD test, a device connects to the car’s OBD system to assess the operations of its emissions equipment.

For an I/M240 test, a technician uses a dynamometer to examine the vehicle’s exhaust gases in a simulated driving setting. Whatever the test used, your car will either pass or fail. While a good deal of vehicles pass, certain models – particularly, older cars that have fallen behind on maintenance – have a higher likelihood of failure due to the following issues.

Old Motor Oil

Changing your motor oil gives your engine fresh lubrication. As oil degrades, it produces more hydrocarbons, which end up in the atmosphere and eventually get detected by an emissions test.

For drivers who have spent weeks or months delaying an oil change, you may see less-than-desirable results if you go for an emissions test over that period. Excluding other potential issues, replacing the oil may be all you need to do to pass.

Too Much Fuel

The engine’s combustion process – essential for powering your car – requires a specific air-to-fuel ratio. When the fuel ratio is too high, the combustion process leaves extra fuel, which then passes through your exhaust system and can alter the results of an emissions test.

What causes an excess of fuel?

  • A malfunctioning fuel injector or fuel metering, often going back to an onboard computer
  • A faulty O2 sensor
  • A faulty mass airflow sensor (MAF), which can’t regulate the air-to-fuel ratio

In all these instances, not only will your car fail an emissions test, but it may also have difficulty accelerating, experience a loss of power or overheat, which can lead to engine failure.

Issues with the Spark Plugs

Also tied to the combustion process, spark plugs help you start your vehicle and are expected to “spark” or fire in a specific sequence. When the plugs have been damaged or have experienced excessive wear, they may misfire or perform incorrectly, which can result in a failed emissions test and a vehicle that won’t consistently start up.

Loose Gas Cap

The gas cap is another aspect of your vehicle that prevents gasoline fumes from entering the atmosphere. When a cap doesn’t seal correctly or feels loose, gasoline and its fumes will leak out into the atmosphere and can cause your vehicle to fail its inspection. Switching to a newer, more secure gas cap often fixes this issue.

Faulty EVAP System

More complex than a gas cap, the Evaporative Emission Control System (EVAP) also helps halt the release of gasoline fumes into the atmosphere and ensures they stay within the gas tank. Unfortunately, damage and wear can prevent the EVAP system from performing its best, including cracked or leaking hoses and vents that need to be replaced.

Dirty Air Filter

Air filters also get replaced when you check your oil. When an air filter is dirty, it can’t perform up to par and allows a larger amount of hydrocarbons to enter the atmosphere. Be sure to get your air filter changed every year or every 12,000 miles – whichever comes first – or you risk failing an emissions test.

Check Engine Light is On

Although the check engine light may come on for several reasons, it can indicate your car’s performance in filtering harmful emissions. The light illuminates when the oxygen sensor breaks or your exhaust system is having issues.

Particularly where your exhaust system is concerned, age and wear may be damaging its parts or the catalytic converter may be experiencing performance issues. In addition to the check engine light, your car’s exhaust system is having a problem when:

  • It experiences decreased fuel efficiency
  • You hear a loud, rattling noise when you turn on the car
  • You notice a sulfur or rotten eggs smell

When your car fails its emissions test, you have a period of time to get it repaired and re-tested. As a Certified Emissions Repair Facility, we can help diagnose the issue and recommend any repairs or parts to be replaced. To make an appointment, contact us today.