Feb. 22nd Emissions Troubleshooting: Why Your Car Failed

Emissions tests are important, yet tricky tests that determine whether your car is safe to drive or not–not just for you, but for the environment as well. Failing an emissions test can result in the inability to drive your car until you fix the problem at hand and retake the test. As motor vehicles are a leading source of air pollution, the EPA enforced a strict emissions law that requires vehicles to meet the proper standards. Emissions tests are designed to ensure that levels of toxic gases commonly produced by vehicles do not exceed the limits. To do so, they measure the number of tailpipe emissions that are being produced, looking closely at nitrogen oxide, carbon monoxide, particular matter, non-methane organic gases, and formaldehyde. Before taking your car in for its mandatory emissions test, be sure to know and recognize the reason why it could fail. In this article, we’ve defined some of the leading causes of emissions test failures and how you can avoid them. 

Common Causes of Emissions Test Failures

While failing an emissions test is serious, most of the time, the problem can certainly be fixed with the help of your local mechanic. Here are a few of the most common causes of failed emissions tests: 

  • Worn out spark plugs: Surprisingly, old and worn out spark plugs can be a leading factor in failed emissions tests. When spark plugs begin to fuaunction improperly, they can cause an increase in emission gases. 
  • Leaking gas cap: A relatively easy fix, a leaking gas cap can lead to a failed emissions test. If this occurs, you’ll want to invest in a new gas cap that properly seals the tank. 
  • Defects in the EVAP system: If the EVAP system–evaporative emission control–is not properly functioning, gasoline vapors can begin to come out of your vehicle’s tank. Usually, a leak in the hose or vents can cause the EVAP system to malfunction. 
  • Malfunctioning catalytic converter: Before you take your emissions test, it’s highly recommended that you have your catalytic converter inspected. If not working properly, your catalytic converter can cause numerous problems for not only your car, but your emissions test as well. If damaged, your catalytic converter can’t turn toxic gases into ones that aren’t harmful to the environment.

Before taking your vehicle in for its emissions test, it may be ideal to take your car in for a routine maintenance check-up. By doing this, your mechanic and double check to see if all your car’s functions are working properly and are up to standard for an emissions test.