Back to all

Why did my vehicle fail its emissions test?

October 27, 2024

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 Wyoming
4315 Clyde Park Ave. SW
Wyoming, Michigan 49509
616.534.8643

More articles from Tuffy Wyoming

Smooth Operator (Shock Absorbers)

October 27, 2025

When you are comfortably headed down the road, you may not realize how many of the imperfections in the driving surface are being smoothed out, so you hardly feel most of them. You can thank your shock absorbers for a lot of that comfort, and its important to make sure you keep your shocks in go... More

A "Mounting" Problem (Motor Mounts)

October 23, 2025

You know how heavy your engine and transmission are, so you can imagine how tough the parts that hold them onto your vehicle's sub-frame must be. Not only must they support the weight, they also have to isolate vibrations and noise from the passenger cabin. Pretty tall order, wouldn't you say? ... More

Don?t Meddle with the Pedal (Brake Caliper Replacement)

October 12, 2025

If you drive a newer vehicle, chances are it has disc brakes, and one of the components of that type of brake is called a brake caliper. The caliper allows the pressure from your foot on the brake pedal to eventually move brake pads against discs in your wheels, which then slow and stop your veh... More