How long have you called Denver home? If you were around in the 1970s or 1980s, you might remember the brown cloud. As we continued to industrialize our city, the population moved outward and began developing suburbia. That meant more driving for all of our daily needs.
The EPA adopted the Clean Air Act to establish standards on air pollution from both factories and vehicles. But even with this law, Denver’s air pollution was visibly noticeable, partially because the city sits in a bowl-like valley. With mountains on one side and the Platte River Valley on the other, a temperature inversion traps pollution inside this bowl, creating a “brown cloud” of unhealthy air.
While policies continue to work at keeping this brown cloud under control, it hasn’t gone away. Experts say that the brown cloud has been replaced by thick smog, with the EPA changing our overall rating recently from “moderate” to “serious.” In 2018, Denver logged 131 days of poor air quality. And that impacts everyone across the Front Range, especially those with compromised respiratory systems.
Years ago, Colorado set up a program to monitor gas emissions from vehicles. Its goal was to keep the worst 
polluters off of the roads. Several counties require an emissions test to register a vehicle, including:
- Boulder
- Broomfield
- Denver
- Douglas
- Jefferson
- Portions of Adams
- Portions of Arapahoe
- Portion of Larimer
- Portions of Weld
There are exceptions to this rule. If you aren’t sure if this rule applies to you, check with the Colorado Air Care Testing Facility near you to determine if your car needs testing, and how often you should take it in.
What an emissions test checks for
An emissions test is designed to ensure that a vehicle isn’t producing unacceptable levels of toxic gases. Tests are designed to measure the amount of emissions coming from a car’s engine. It’s a simple test that checks the pollutants being emitted from the tailpipe and being released into the air supply. It measures:
- Nitrogen oxide (NOx)
- Carbon monoxide (CO)
- Particulate matter (PM)
- Non-methane organic gases (NMOG)
- Formaldehyde (HCHO)
If your car passes, you can register your vehicle and drive it on the roads.
But what if your emissions test fails?
Here are the most common reasons a car will fail an emissions test.
Your car needs an oil change. An oil change is considered to be regular maintenance. It’s something that you should perform regularly, whether you drive regularly or not. Clean oil has fewer hydrocarbons in it, and helps keep your engine cleaner. A clean engine means cleaner emissions output. Check with your vehicle’s manufacturer, or refer to your owner’s manual to determine how often your oil should be replaced. Remember, this is based on time and miles driven. Even if you work from home and your car sits idle most days, it doesn’t mean your car doesn’t need fresh oil on a regular basis.
Your car has a rich air-fuel mixture. This is often caused by a malfunctioning injector or a faulty oxygen sensor. Check and replace both of these items before checking the emissions once again; this fixes the problem in a lot of cases. If the system continues dumping too much gas into the system, it will burn out the catalytic converter. Bringing it into our shop for a thorough checkup can find this and fix it if it’s the problem.
Your spark plugs are worn. When spark plugs wear down, they produce incomplete combustion. The spark plug creates electricity that ignites the air-fuel mixture inside the engine. The spark plugs create the motion inside the piston, and continue to provide power to keep your vehicle moving. When this process is incomplete, it can impact how much your car is emitting. Changing your spark plugs may be all that is needed to get your car back on the road.
Your car’s gas cap is leaking. This is a simple issue you can fix yourself. First, inspect your gas cap to see if it’s properly sealed. Tighten it if necessary. If you notice a leak, replace the gas cap and test your vehicle’s emissions again.
Your car’s air filter is dirty. When a vehicle’s air filter clogs, it can increase the levels of hydrocarbons being emitted from your car’s engine. Most manufacturers suggest replacing your car’s air filter at least once a year. If you don’t remember when you last had it changed, consider replacing it and trying the emissions test again. This should be a part of your regular maintenance plan to ensure your vehicle is in the best condition possible.
Your car’s evaporative emission control system (EVAP) is defective. When a vehicle’s EVAP system isn’t working correctly, gas vapors will move from the gas tank and add to the pollution levels in the atmosphere. This is often caused by a leak in the hoses or vents, causing the EVAP system to work improperly. While this can be difficult to track, a thorough diagnostics test can often reveal where the problem lies.
Your car’s check engine light is defective. While every light on your dashboard is important, the check engine light is one you should never ignore. It can signal many different problems with the way your engine operates. Occasionally, the check engine light itself may malfunction, and be the cause of why your car is failing the emissions test.
The best way to proceed is with proper maintenance and an inspection by a professional mechanic
While a failed emissions test isn’t a sign your car has major systems problems, it is a warning of an issue that needs solving.
While regular maintenance can keep your vehicle in top driving condition, it’s an ongoing process.
By stopping by regularly, we can ensure your vehicle is in good condition, and will give you peace of mind, knowing your car will be reliable no matter where your travels take you.
How can we help you maintain your vehicle for years to come?