Why Your Car Could Fail an Emissions Test

As society leans toward greener methods for production and manufacturing, governments need to take stock of human-made creations that contribute the most to air pollution. Unfortunately, one of the most significant producers also happens to be vital to transportation. Unregulated vehicles release a plethora of toxic and harmful gases into the atmosphere. Therefore, to try and curb the level of environmental harm, some state governments have begun requiring motorist to bring their vehicles in for an emissions test. These tests are designed to measure the amount of pollutants being emitted from your vehicle's exhaust. If you pass an emissions test, then there is really no problem or hassle, but a failed emissions test can lead to issues and unexpected expenses.

Vehicles that fail the emissions or smog test cannot be registered with the DMV, meaning that if your car fails, you cannot get a license plate for it. You will be required to repair any issues and have your vehicle retested before registration can occur. In most instances, an inspector will give you a point by point evaluation of your emissions system, which should let you know if you are dealing with a major or minor repair. However, how do you know if the tests are accurate, and how do you avoid failure in the first place.

How the Tests Work

While some may question the integrity of emissions testing, the EPA and other regulatory bodies stand by the accuracy of this type of testing to manage the pollutants stemming from the exhaust system of your vehicle. There are two essential emissions tests: (1) the OBD or on-board diagnostic check and (2) the I/M240 dynamometer test. The OBD check is performed on vehicles from 1996 to current models. It essentially connects to the OBD system of newer cars and measures to see if all emissions equipment is working correctly. The I/M240 test is performed on vehicles manufactured between 1981 and 1995, and its tests are more involved. Utilizing a dynamometer that simulates driving on road conditions, the vehicles exhaust gases are captured and analyzed to determine a pass or fail.

Why Do Cars Fail Emissions Tests?

When people buy a used car and are required by state law to take it in for testing, they can become anxious. After all, no one wants to purchase something and then be told they can’t use it, or that it will cost them additional money to bring it up to code. However, while an emissions test may make you nervous, there are at least seven reasons that a failure may occur, and not all of these reasons are costly.

Top Seven Reasons Why Cars Fail

1. Loose or leaking gas cap

As failures go, a leaking gas cap is probably one of the least expensive problems to fix. Especially in older vehicles, the seals on gas caps can wear away, which can potentially lead to excessive fumes being released from the tank. However, you probably don’t even need a mechanic to fix this issue, just purchase a new cap made for your make and model and install it.

2. Dirty air filter

How long has it been since you replaced or even thought about cleaning your air filter? Honestly, cleaning or replacing the air filter should probably be one of the first things you do after purchasing a used vehicle. When these items are too dirty, they can lead to the production of high-levels of carbon monoxide, which can cause a failed emissions test.

3. Worn spark plugs

While small, spark plugs are among the most critical parts in your engine, unfortunately, they can also lead to a failed car emissions test. You should replace the spark plugs if they exceed their mileage interval. This will help restore performance and potentially better your gas mileage while lowering emission pollutants.

4. Damage to the catalytic converter

The catalytic converter might be the most crucial piece of equipment in your engine when it comes to controlled emissions. The job of this device is to convert toxic gases into nontoxic emissions, thereby protecting the environment and public health. A damaged catalytic converter will most definitely cause a failed emissions test. Therefore, you’d be better off getting it checked out before the test.

5. EVAP defects

A cars evaporative emission control or EVAP system ensures that gasoline vapors remain contained inside of the cars fuel tank. If this system is damaged, then harmful gases are released into the atmosphere. Unfortunately, since there are multiple hoses and vents that make up this system, the problem can be hard to track down, which can lead to costly repairs.

6. Rich-running system

A rich air-fuel mixture can also lead to an emissions test failure. The cause of such a rich-running system can be anything from a faulty oxygen sensor to malfunctioning injectors. However, it is essential to sort this issue out sooner rather than later to avoid damaging the catalytic converter. A rich-running system can dump excessive amounts of raw fuel through the system and damage or clog the catalytic converter.

7. Defective check engine light

Unfortunately, as accurate as the emissions test can be, there are times where a failure occurs in a system that is actually working correctly. There are times where a car will have a faulty or defective check engine light, which might cause a failed emissions test. Thankfully, these lights are often cheap fixes, but if you are unaware of the defect, you may spend a lot of time rooting out the problem.

Avoiding Failures

The only way to prevent an emissions test failure is to take care of your vehicle. Sticking to a proper maintenance and inspection schedule goes a long way. However, it is also essential to know your limitations. Many car owners think they can DIY their way through everything, and in many circumstances that is true; however, don’t avoid professional inspections to ensure that any work or repairs you performed are up to par.

The only surefire way to learn how to pass an emissions test is to know what, if anything, is wrong with your car before the test. So, take your vehicle to a mechanic, get it inspected and then pick up those essential components to work your DIY magic. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

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