Why did my vehicle fail its emissions test?
August 11, 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.
TLC Custom Exhaust Brakes & Tires
1735 N Main St
Royal Oak, Michigan 48067
248-541-8300
http://www.tlcautocareroyaloak.com
Need Service?
More articles from TLC Auto Care

Let's Clear Some Things Up (Headlight Restoration)
January 25, 2026
You know how exposing your skin to sunlight can cause sunburn and other unhealthy things. Sunlight can also create major problems for your headlights. After they've been exposed to ultraviolet light, acrylic headlights can yellow and fog due to oxidation. And when that happens, less light can ... More

A Most Important Part (Serpentine Belt Replacement)
January 18, 2026
Your vehicles engine is an engineering work of wonder with many complex parts working in harmony to get you down the road. One of those simple but important components is called a serpentine belt. It is driven by a pulley on the engine and transfers that power to many of your engines most importa... More

Conventional or Synthetic? (Switching to Synthetic Oil)
January 11, 2026
If you keep up on technology trends, then you may be intrigued about synthetic motor oil. It was introduced in the 1960s when Mobil came up with it. Mobil's oil was different from conventional motor oil because it was first broken down to its basic molecules. Then, Mobil removed additional imp... More
