Back to all

Why did my vehicle fail its emissions test?

March 30, 2025

We all want to breathe clean air and keep our planet green.  One of the ways to do that is by requiring all vehicles with internal combustion engines to pass an emissions test.  That’s because these vehicles can be big polluters.  

Everyone wants their car to pass the test so they can continue their day-to-day driving routine.  But then comes that one day when they tell you your vehicle has failed.  Why does that happen?

One of the most common reasons is that your gas cap is leaking or loose (or maybe you don’t even have one on your vehicle!).  The gas cap is supposed to seal in vapors, but sometimes its seals or gaskets dry out or crack. Replace it, and you’re good to go.

Another common reason your vehicle failed the test is that your catalytic converter isn’t doing its job. It is supposed to convert toxic gases from your engine into ones that don’t pollute the air.  There are many reasons the catalytic converter may not be working.  It may be physically damaged, or the steady flow of exhaust gases has fouled the converter. 

You may have a bad oxygen sensor. It’s supposed to measure how much oxygen is in your exhaust.  This can cause the air-fuel mixture to be too rich, resulting in too many hydrocarbons in the exhaust. Your ignition system may also have problems, such as worn-out spark plugs.  Dirty fuel injectors can contribute to excess emissions.

Believe it or not, a dirty engine air filter may be the culprit. If it hasn’t been replaced for a while, your vehicle may be emitting too many hydrocarbons -  something that will cause your vehicle to fail the emissions test.

You can usually avoid a failed emissions test by maintaining your vehicle regularly.  The best way to do that is by bringing it to our trained technicians, so your vehicle gets the service it needs, scheduled and non-scheduled.  Plus, you’ll be doing your part to keep our air clean.

Tuffy Grand Rapids
610 28th St. SE
Grand Rapids, Michigan 49548
616.452.4425

More articles from Tuffy Grand Rapids (28th St.)

Putting a Stop to Brake Problems (Brake Service)

June 9, 2025

It's safe to say that most drivers take their brakes for granted. You press on the brake pedal and the vehicle slows down or stops. It's easy to see why it is so important for your vehicle's brakes to be working correctly. Brakes are an important safety feature of any vehicle. When it comes to... More

When it Comes to Air Filters, Change is Good (Clogged Air Filter)

June 2, 2025

Engine air filters may not seem like a big deal, but when theyre clogged up with dirt, dust, and insects, your engine could wind up choking for air and not delivering you the power and performance it was designed to give. There are actually a couple of air filters in your vehicle. One filters th... More

Bump in the Road (Alignment)

May 25, 2025

There's something you can do that helps your tires last longer, wear more evenly and your vehicle handle better. "Sign me up," you say! Wondering what that is? It's aligning your wheels, and it will literally point you in the right direction when it comes to a better and safer driving experience... More