Why Your Car Failed Emissions

We love our cars. When they’re running great, we depend on them to get us to where we need to go. If you’ve ever been without a car, you know the freedom they represent. 

But with great freedom comes great responsibility. Vehicles emit a host of toxic gases from combustion in the engine, which come right out the tailpipe and into the atmosphere. 

Emissions tests are designed to ensure these gases are released at a safe limit, improving air quality and the environment. Therefore, these tests are government regulated. emissions tests in colorado

You won’t legally be allowed to drive your vehicle if it fails its emissions test. 

Whether you’re a “fix it when it breaks,” or “prevent a breakdown in the first place” kind of driver, the required emissions test will be the legal determiner if you can get your vehicle registered and drive it on public roads. 

How do I get an emissions test?

In Colorado, there are two options for getting a gas powered vehicle emissions test: roadside and at an Air Care Colorado Station. Find a testing station and plan your visit. 

Why did my car fail emissions?

By keeping up on scheduled maintenance, your vehicle will usually pass its emissions test with flying colors. 


If you’re wondering what caused your car to fail its emissions test, it usually comes down to one of these things: 


1. Check engine light

Oftentimes if the check engine light is on, your vehicle won’t pass the test. Since the check engine light can come on for a variety of other reasons not related to emissions, it’s a good idea to have it diagnosed and repaired before you get your test. 

2. Leaking gas cap

If gas cap seals are worn and allowing fuel vapors to escape, the vehicle will fail its emissions test. This is one of the best-case fail scenarios since gas caps are relatively cheap to replace. 

3. Issue with the EVAP system

The evaporative emission control system (EVAP) includes hoses, lines, seals and vents that can leak fuel vapor if working improperly. 

4. Faulty catalytic converter, fuel injector or O2 sensor

These lead to contaminants or rich air-fuel mixture out the tailpipe. 

5. Dirty air filter

Yes, while rare, the air filter can actually cause a vehicle to fail its emissions test. 

6. Worn spark plugs

Another reason why regular and scheduled maintenance is important. 

What happens if my car fails emissions?

If your car fails emissions, don’t worry. There are many reasons this is the case, so it’s best to take a step-by-step approach: 


1. If you want, you could first try replacing your gas cap. 

Purchase a gas cap at a local parts store. After replacing it, drive your vehicle and see if the check engine light goes off. 

2. Next, schedule an appointment with an emissions repair mechanic

They’ll diagnose the cause for the failed emissions test and give you recommendations on how to repair your vehicle.

3. Decide on repairs.

This is easier said than done. If you aren’t too fond of your vehicle or are feeling ready for a new one, this may be your breaking point. But oftentimes emissions repairs are no big deal--meaning, it’s worth fixing and getting back on the road ASAP. 


The Service Advisors at Community Auto in Fort Collins will professionally walk you through your options and help you choose the best repair. Don’t hesitate to call with any questions!

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