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

A Fluid Situation (Check Fluid Levels)

November 9, 2025

There's one fluid in your car you are always careful to keep at a certain level: the fuel. If you don't have fuel, you're not going anywhere. Your vehicle has other fluids which are vitally important to proper and safe operation, too. So, here's a "level" headed approach to those "other" fluids... More

If You Drive Like a Maniac (Aggressive Driving is Bad for a Vehicle)

November 2, 2025

When someone mentions driving like a maniac, they're not talking about you, surely? Besides the safety issues of aggressive driving, you should know that your vehicle will last a lot longer if you'll just mellow out a little. Here are four traits good drivers follow if they want their vehicles t... More

Go Big or Go Home: Upsize Your Wheels at Tuffy Tulsa

October 27, 2025

A lot of us TULSA drivers like our vehicles to reflect our personalities. We're picky about color and body style. We'll customize anything from floor mats to window tints to license plates. One popular way for OK motorists to customize a vehicle is to get new wheels.Wheels come in thousands of d... More