How Can I Tell if My Car Needs Emission Test? – Guide

How Can I Tell if My Car Needs Emission Test? – Guide

Depending on your area, some people refer to it as a smog test or emission inspection.

The United States of America was the country to come up with the emission test as a law; later other states like Australia adopted it.

How Can I Tell if My Car Needs Emission Test? – Guide

The following is all you need to know about car emission tests.

What is a Car Emission Test?

A car emission test checks your vehicle’s exhaust emissions and whether they conform to the state’s emission legal requirements.

When you take your car for an emission test, it will be connected to the testing system using the OBD port of your car. A sensor is attached to the tailpipe if your car has no OBD port.

Knowing When Your Car Needs an Emission Test

In some states, it is a requirement by law to take your car for an emission inspection.

When you take your car for the emission test, it will undergo several procedures to determine the nature of its emissions.

Most car owners fail to pass this test.

As a result, they have to take their car for a thorough mechanical check-up to fix the causes of bad emissions, thus restoring your car to its top performance.

Performing an emission test for your car is essential.

As a car owner, you will tell when your car needs this test.

When the check light appears, you experience weak acceleration, poor fuel economy, and emission of bad smell are some common symptoms that you need to perform an emission test.

Here is a detailed explanation to tell you when to perform an emission test for your car.

The Appearance of the Check Engine Light

Some cars have a separate light that lights up when there is a problem with the emission, it is the emission light.

But for most cars, when there is a problem with the emission, the engine check light will turn on on the dashboard.

It is necessary to check the car’s user manual to know which light will give you a clue about emission issues.

The emission light could indicate a sensor error, a bad exhaust fume recirculation valve, and a faulty vacuum hose.

Consider checking these areas as soon as the emission check light appears. It is easier to identify the error using a computer. Doing this will direct you to the faulty part.

You can keep driving with the emission light on as long as other parts of your engine run smoothly.

But the longer you ignore the light, the issue might develop and even damage other parts of the engine.

The emission light on the dashboard is an early call to determine the nature of the emissions from your car.

Doing this determines whether such emissions are clean or harmful to the environment.

Poor Fuel Economy

Problems with the exhaust system lead to high fuel consumption.

No one likes it when their car consumes more fuel, and mostly, everyone pays attention to the consumption rate of their cars.

When you note that the rate at which your car consumes fuel is going up, consider performing an emission system.

The oxygen sensor checks the condition of the exhaust gases from the combustion chamber. This sensor detects if the exhaust fumes are rich or lean.

If your oxygen sensor is faulty, chances are high that it will not account for the nature of the exhaust emissions.

Your car will emit fuel-rich exhaust fumes. If this happens, the rate at which your truck consumes fuel will go up.

The fuel injectors perform the role of spraying fuel into the combustion chamber.

With time, they become faulty, leading to over/underfeeding fuel into the combustion chamber.

When overfed, the rate at which your car consumes fuel will go high, and it will not pass the emission test.

Mass Airflow sensor checks the air in the combustion chamber as it mixes with the fuel.

Sometimes it gets faulty and fails to monitor air flowing into the combustion chamber.

When this sensor is faulty, more fuel will flow into the combustion chamber than oxygen. The excess fuel will move to the exhaust system.

In such a situation, consider performing an emission test.

Emission of Bad Smell

When you start feeling the smell of sulfur, rotten eggs, or raw fuel is a clear indication that there is a fault with the emission system.

The smell is not only unpleasant but is very dangerous to your health.

When your tank is full of fuel, you will feel a bad smell, but as the fuel level goes down, the smell disappears.

But when it persists, it indicates fuel leakages within the engine.

The emission of bad smells can reduce your car’s fuel efficiency and indicate a problem with your emission system.

In such a scenario, consider performing an emission test. Doing this will assure you of the nature of your car’s emissions.

Weak Acceleration

When you feel that your car is becoming sluggish whenever you press the acceleration pedal is a clear indication that there is a problem with your emission and you need to perform an emission test.

How Can I Tell if My Car Needs Emission Test – Guide

Weak acceleration is usually accompanied by a power loss or even stalling when on the highway.

You will tell acceleration issues when your car jerks, you stale, or you even lose power. Such problems can be risky and escalate into major problems if not checked in time.

The fuel pump generates pressure to move fuel from the tank to the engine. When it becomes faulty, the rate at which fuel flows to the engine will reduce.

If such happens, you will experience a weak acceleration.

Fuel injectors release fuel into the cylinders at the right quantity and time. When faulty, it might release too much fuel into the cylinder.

Fuel-rich combustion will occur, leading to high emissions. 

Faulty spark plugs, glow plugs and other engine issues also lead to weak acceleration. Weak acceleration is an indication of developing engine issues worth paying attention to.

Consider performing an emission test as soon as your car starts to experience problems with the acceleration system.

If you care about your car and love your surroundings, you can perform an emission test at home.

You only need to have an emission analyzer that will analyze and let you know the nature of gases coming from your emission system.

A home emission test is the best option when preparing to take your car for emission test certification. It also comes in handy when you note any of these symptoms from your car.


An emission test is a requirement in some states, but it is essential to perform it if you take care of the environment.

This test determines how friendly your car’s emissions are to the environment.

The emission test entails the OBD inspection and exhaust gas analysis. The OBD inspection checks the efficiency of the ECU system.

The ECU system is the computer component that controls the engine, transmission, emission system, and other vital parts of a car.

On the other hand, the exhaust gas analysis checks if your car’s exhaust emissions are harmless to the environment.

Your car will require an emission test, and you will know this when it starts to give various signs. If you note any signs in this guide, consider performing an emission test.