Back to all

Why did my vehicle fail its emissions test?

December 29, 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 Tulsa
4817 W. 41st Street
TULSA, OK 74107
918-550-3277
http://www.tuffytulsa.com

More articles from Tuffy Tulsa

Stopping "Brake" Downs (Brake Pad Replacement)

March 30, 2025

If someone tells you to put the brakes on something, you know it means stop. And stopping is one of the most important safety maneuvers you can do in any vehicle. That means your brakes have to work properly. Let's face it. You stop dozens of times every time you drive. And over time, that t... More

Tacky or Techie? The Tachometer.

March 23, 2025

There's a gauge that many vehicles have that says RPM on it. And there are a lot of people who either don't pay any attention to it or don't even know what it is. Here's why it's a good gauge to know about. It's called a tachometer, and that "RPM" label means it is measuring how many revolutions... More

I NEED All Wheel Drive (Pros and Cons of AWD)

March 16, 2025

So winter has arrived and you don't feel confident in how your 2-wheel drive vehicle does in the snow and ice. You envy all those people with all-wheel-drive (AWD) and 4-wheel-drive (4WD) cars, trucks and SUVs. You start thinking, "I need one of those. I'll be able to go anywhere without any w... More