how to tell if your car will pass emissions

Learning how to tell if your car will pass emissions test can save you from a lot of trouble and headache.

Since emissions testing is a typical requirement for car ownership in the United States, the term may be familiar to many people.

Moreover, this test may be essential for the first time for some individuals when relocating or acquiring a new car.

So, if emissions testing is mandated in your state, it is natural to wonder, “Will my car pass emissions?” Thankfully, there are ways to confirm.

Simple checks for things like no check engine light, clean air filters, a fully charged battery, and no gas cap issues may help your car pass emissions

What are Car Emissions?

what are car emissions

 Cars emit various contaminants into the air.

Some of the most common ones include:

  • Nitrogen oxides
  • Carbon monoxide
  • Hydrocarbons
  • Particulate matter

By adding to the air pollution, these emissions can have a devastating effect on the environment.

Moreover, they can have a direct impact on your health, particularly making respiratory issues more severe.

To prevent excessive pollution from being released into the air from automobiles on the road, governments implement emissions standards and testing systems

What is Involved in a Car Emissions Test?

what is involved in a car emissions test

Every engine produces emissions, and there is typically a cap on the amount of pollution your car may produce in any given area.

In the past, this inspection required driving your vehicle onto a dynamometer (a car treadmill) and having several pieces of equipment attached to your exhaust system.

That is much easier now: The onboard diagnostic II port is a common electrical input in vehicles manufactured after 1996 and is normally located toward the bottom of the steering column.

A visual inspection will also be performed. 

How the Testing System Works?

The on-board computer is programmed to alert the driver to any problem that could prevent the vehicle from meeting federal emissions standards.

Technicians also play a role by monitoring cycles for different systems.

how the testing system works

There may be a dozen screens, and the computer is responsible for monitoring the integrity of all the administrative apparatus.

Depending on how well these monitors function, you may or may not pass an emissions test.

If the bulk of your checks passes, then you are good to go. 

An Important Consideration

The OBD-II interface is unnecessary in some locations.

For instance, the RapidPass program in Virginia collects exhaust gas samples at roadside monitors.

If you pass, you will not need to visit an emissions station; you will receive an alert instead

How to Tell If Your Car will Pass Emissions?

So many factors go into determining whether or not your car has a good chance of passing the emissions test.

For instance: 

Overall Maintenance

How well your car has been maintained will give a clue about the likelihood of passing the emissions testing.

Maintaining your vehicle with regular oil changes, air filter swaps, and tune-ups keeps it running smoothly and efficiently. 

The Status of Check Engine Light

the status of check engine light

The Check Engine Light should never be ignored! Get it checked out at a reputable service center to address the problem appropriately.

When the emission control system in your car is malfunctioning, the Check Engine light will come on to warn you.

It indicates that you are likely generating far more dangerous emissions than the EPA allows.

The Check Engine light must be off in order to pass a smog check.

If you take your car in for inspection while the light is on, you will receive a failing grade.

To avoid wasting time and money, it is best to have a professional take a look at your car as soon as the warning light turns on.

Fact: More wear on the catalytic converter and other costly problems may result from driving your automobile with the check engine light turned on. 

Consider the Driving Experience

Make sure your car has a good idling and driving experience.

Smog test results might be impacted by concerns about the vehicle’s engine performance. 

Smooth Gas Cap

smooth gas cap

You are likely to pass emissions if the gas cap does not seem tight.

If it feels tight, do not risk it.  Instead, head to the auto parts store and pick up a replacement gasoline cap.

Keep in mind that many aftermarket gas caps fall short of OEM standards and could end up causing more harm than good. 

Good Quality Battery

Having a good quality battery installed on your car may also help increase your chances of passing an emission test.

So, be sure to replace the battery with a better model.

The OBD-II self-test component of the smog test is computer-based, so if you often use a jump starter, you may fail. 

No Leakage in the Fuel System

no leakage in the fuel system

A leak in the fuel system (perhaps caused by the gas cap, but likely more serious) means trouble.

Your car’s system detects fuel evaporation and alerts you with a check engine light, ultimately resulting in a failed inspection.

A defective gas cap is often the root of the problem. 

The Condition of the Air Filter

Any problems associated with the air filter can directly affect the outcome of your car emissions test.

Poor engine performance caused by a clogged air filter contributes to pollution. Fixing this is necessary to avoid a failed test. 

No More Misfires

no more misfires

Misfires and other problems might be caused by spark plugs that have seen better days.

The dashboard warning light might go on for some of these problems, but not for others.

A failed emissions inspection could be the result of worn-out spark plugs, even if the automobile runs OK otherwise. 

The Condition of Catalytic Converters

If those catalytic converts are in good condition, you have a good chance of passing your test.

Catalytic converters help reduce emissions by turning toxic compounds into less dangerous ones, but their effectiveness declines as they age or become damaged.

Dirt, debris, and exhaust pollutants accumulate over time, eventually blocking them.

Slow engine performance and other problems could be the result. If the catalytic converters fail, the vehicle will also fail the emissions inspection. 

Take a Practice Test

When you believe you have everything in order but are still confused, you may benefit a lot by undertaking a practice test.

The state will not “notice” this because the smog check is being conducted outside of their system.

take a practice test

Taking this step can help you avoid the hassle of getting your car “tagged” by the state and going through a potentially time-consuming process just to have it smog-ready.

Fact: Remember that if you are labeled as a "gross polluter," you are required to visit a "STAR" repair station, which will charge more than a conventional repair station.   

A Good Air Fuel Mixture

Too much gasoline is being sucked into the engine and burned on each stroke if your car operates with a rich air-fuel mixture.

In comparison to a lean mixture, this can increase power slightly, but at the expense of fuel economy and exhaust pollution.

Exhaust giving out a sulfurous or “rotten eggs” smell is a sure sign of a dangerous blend.

In this situation, taking your automobile in for an emissions inspection could result in a failed test. 

The Importance of Working with a Technician

importance of working with a technician

When not sure, working with a professional is the best way to confirm whether your car will pass emissions.

Get your automobile checked up by a certified emissions technician.

Emissions repair is very complicated and takes years of experience, so your normal shop may only be able to do routine maintenance.

Fact: To become an emissions repair tech, many jurisdictions now require a four-year degree in automobile technology, so look for the right person. 

How Can a Good Technician Help with Emissions?

good technician help with emissions

A mechanic can assist you to figure out why you failed the emissions test if the problem is more complex than just a faulty gas cap.

They can utilize diagnostic equipment to find out which screens have failed the inspection and have them fixed.

However, these methods just identify the issue and provide no guidance on how to fix it.

It is the mechanic’s knowledge and experience that determine the best course of action.

Always remember that it is just a myth that every professional is equipped with a magic instrument that tells them what to do.  

Fact: Your vehicle may also fail the smog check if it is smoking or overheating, as high levels of hazardous emissions can result from both excessive engine heat and exhaust smoke.


So, how to tell if your car will pass emissions?

It does not have to be tricky because all you have to do is ensure that it is in good condition, has no check engine light turned on, and has no issue with air filters and battery.

If you are not sure about anything, it is best to work with a certified technician to get your car checked.