Back to all

Why did my vehicle fail its emissions test?

May 18, 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 Tire & Auto Perrysburg
27140 Oakmead Dr.
Perrysburg, Ohio 43551
419-873-8330

More articles from Tuffy Perrysburg

Put the Brakes On! (Brake Caliper Replacement)

May 11, 2025

Keeping your vehicle's brakes in top shape is one of the most important things you can do for your safety and those on the road with you. Most drivers know a little about brake pads and rotors but maybe not so much about another brake component called the calipers. Disc brakes work by a mechanica... More

Flat Tire? Three?s the Charm (Tire Repair)

May 4, 2025

For most drivers, at some point youre going to have a flat tire. Depending on how it was damaged, it may have to be replaced. But sometimes, a repair will do the trick, as long as the puncture isnt on the sidewall and the hole is smaller than inch/6.35mm in diameter. Here are the three common w... More

The Puzzling Puddle (Leaks Under Vehicle)

April 27, 2025

Ever notice a little spot of liquid under your vehicle after you've parked in your driveway or garage? It may have been something as simple as water left from air conditioning condensation. But then again, it could be a sign that there's trouble brewing in one of your vehicle's systems. You can ... More