Emission Test Myths: These That You Know and These That You Don’t

Posted on 20 July, 2017

In most states, a vehicle’s exhaust emissions is checked every year during the annual inspection period. Unfortunately, lots of cars fail these tests and that’s awfully annoying because if your car doesn’t “pass inspection,” you can’t legally drive it.

Possibly because of how important it is to pass the annual emissions test, all sorts of myths have sprung up of “ways you can help.” We spoke with a technician at Federico Kia of Wood River, a local Kia dealer in Wood River, IL, and reviewed some of these myths; he debunked most of them. For example:

Warm up your car by driving it hard before the test

Warming up your car will get your motor running in its best overall condition and allows your catalytic converter warm up properly. However, there is a myth running around that says you should drive around like a maniac for an hour before you bring your car into be tested. According to our technician, this is just silly. Just warm up your engine by driving it normally for 10 minutes or so and drop it off.

Adding fuel cleaners will help you pass

There is some truth in this. Fuel cleaners will help your car’s engine get cleaner. They burn the gunk stuck to your engine’s valves and head, and when it burns, your engine runs cleaner. It’s a good idea to use a fuel cleaner once in a while, but it’s a bad idea to put it in the car just before you are taking your car to get tested. This is a myth that has existed for years.

Get a tune-up

OK, there is some truth to this one. If your engine is running poorly, it may fail an emissions test. Getting your car tuned-up is usually pays off in other ways. Not only will it increase your chance of passing an emissions test, your vehicle will run a lot smoother and you’ll get more miles per gallon.

Replace the catalytic convertor

Many inspection stations suggest that installing a brand new catalytic converter on your car may help you pass an emissions smog test.  According to our expert, if your catalytic converter is going bad then replace it, but don’t replace it “just because it might help.” This is just nuts.

Pull Out Your “Check Engine” Light

This is one of the silliest things to do. The check engine light is required to be working when the technician tests the vehicle. If the tech doesn’t see the light because someone tampered with it—your car will automatically fail the inspection. If your check engine light is on, it is best to find out why and then repair it.


In general, don’t play any tricks to pass any emissions test. To help you pass, always follow the manufacturer’s guidelines for service intervals and keep your car in tune. If your car doesn’t pass, there is likely something that is wrong and your mechanic can provide advice on what to do.