An emissions test measures the levels of various pollutants a vehicle releases into the atmosphere through its exhaust system. The most common pollutants checked include carbon monoxide — a colorless, odorless gas that can be lethal in high concentrations, and nitrogen oxides, which contribute to smog and acid rain.
Meanwhile, vehicles must meet specific emissions standards that limit the amount of these and other pollutants they can emit. The criteria for passing or failing depend on these regulatory limits, which may vary by location and vehicle age.
Why Do You Need Emissions Tests Before Driving On A Road?
Emissions testing is a procedure that checks if a vehicle’s exhaust emissions meet the required environmental standards set by government regulations. Vehicle registration must pass these tests to ensure they aren’t contributing excessively to air pollution, which can harm public health and the environment.
Additionally, passing emissions tests is often legally required to keep a vehicle on the road. Failing to meet these regulations can lead to fines and restrictions on vehicle use.
4 Common Reasons Used Car Failed Emissions Test
There are many reasons behind a failed smog test emission; some are easily visible, such as dirty air filters, while others are hidden.
1. Faulty Oxygen Sensors
Oxygen sensors in a vehicle measure the amount of oxygen in the exhaust gas. These sensors are crucial for the car’s computer to balance the fuel mixture.
A faulty oxygen sensor can send incorrect data, causing the engine to burn too much or too little fuel. This imbalance often leads to higher emissions and can cause the vehicle to fail its test.
2. Issues With The Catalytic Converter
The catalytic converter is a device that reduces harmful emissions from the vehicle’s exhaust. It converts pollutants like carbon monoxide, nitrogen oxides, and hydrocarbons into less toxic substances such as carbon dioxide and water vapor.
If the catalytic converter is damaged or not working correctly, the efficiency of this conversion drops significantly, leading to an increase in harmful emissions and a likely failure in the emissions test.
3. Problems With The Fuel System
The fuel system provides fuel to the engine. Issues such as leaking fuel injectors or problems with the fuel pressure can affect the air-to-fuel ratio, leading to incomplete fuel combustion.
Therefore, it reduces the car’s performance and increases the emissions of unburned hydrocarbons and other pollutants, which can lead to a failed test.
4. Malfunctioning Evap System
The Evaporative Emissions Control System (EVAP) captures and recycles fuel vapors from the fuel tank and carburetor. When a leak or a component of the EVAP system is not functioning correctly, these vapors escape into the atmosphere.
Thus, a malfunctioning EVAP system can significantly increase hydrocarbon emissions, a common reason for failing emissions tests. This system is essential as it controls emissions when the vehicle is not running.
3 Steps To Take After A Failed Emissions Test
- Retesting To Confirm The Result: Immediately after failing an emissions test, consider having the test redone to confirm the results. Sometimes, minor issues like temporary glitches in the vehicle’s computer system or environmental factors can affect the test outcome.
- Finding A Qualified Mechanic Or Repair Shop: Look for a certified mechanic or repair shop in emissions repair. Check for certifications from reputable automotive organizations or local regulatory bodies.
- Importance Of A Detailed Diagnostic: To accurately identify the issues, obtain a detailed diagnostic from your mechanic. A comprehensive diagnostic should include checking engine light codes, spark plugs, and gas caps and evaluating the engine’s performance.
Old Car Vs. New Car?
| Aspect | Repairing An Older Car | Purchasing A New Or Newer Used Vehicle |
| Initial Cost | Lower initial expense. | Higher upfront costs are often offset by financing options. |
| Depreciation | Minimal, as most depreciation has already occurred. | Rapid for new cars; slower for used vehicles. |
| Insurance Costs | Generally lower due to the car’s age and value. | Typically higher due to greater value and repair costs. |
| Maintenance Costs | Can be high with frequent repairs. | Lower, especially with warranties for newer cars. |
| Reliability | Decreases with age, possibly leading to extra costs. | Higher, often includes the latest technology and safety features. |
| Environmental Impact | Poorer emissions and fuel efficiency. | Better compliance with environmental standards. |
| Resale Value | Lower due to age and wear. | Higher, especially if well-maintained and sold timely. |
| Long-term Investment | Frequent, costly repairs make it less cost-effective. | Better long-term investment with fewer early maintenance issues. |
What To Do With A Defective Car?
If you’ve had a car that constantly fails an emissions test, it may be time to consider replacing it. The costs of continued testing and repairs may not be worth it. On the other hand, if you just purchased your new or used vehicle, and it keeps failing emissions testing, you will want to take it up with the repair facility and/or the vehicle manufacturer. Though not as common with new cars, people who purchase pre-owned models from a dealership sometimes end up with used car problems that may have no remedy. In some instances, these vehicles have become so problematic that they are referred to as “lemon” cars. It’s always best to be on the lookout for these types of situations and address them through the appropriate avenues.
