What is an evaporative canister filter?
An evaporative canister filter—also known as the EVAP filter or vapor canister filter—is an integral part of your car’s evaporative emission control (EVAP) system. Its purpose is to collect the excess gasoline vapors that build in your fuel tank and convert them into two different substances: hydrocarbons and carbon dioxide.
Once the fuel vapors are converted to these substances, the hydrocarbons are re-distributed into the fuel system via the EVAP purge solenoid. The hydrocarbons are then burnt during the combustion process. The carbon dioxide, on the other hand, flows through the EVAP vent solenoid into the outside air.
The engine control module (ECM) controls the EVAP system and determines when the vent and purge solenoids open. The purpose of this system is to reduce the amount of harmful pollutants that your car produces and to improve the overall performance and efficiency of your engine.
When should I replace the evaporative canister filter on my car?
Although some manufacturers may include a replacement schedule for evaporative canister filters, most do not. That means the only time you should have to replace your filter is when it becomes clogged by debris or malfunctions.
These are the most common symptoms of a faulty evaporative canister filter:
Check engine light (CEL): One of the main symptoms of a faulty EVAP filter is the presence of the CEL. Remember, though, that this light may appear for many different reasons. You’ll have to use an onboard diagnostics (OBD) scan tool to identify the exact trouble code.
Strong fuel smell: If the canister filter fails and can no longer trap excess fuel vapors, you might notice a strong fuel odor in and around your car.
Failed emissions test: If your EVAP filter is clogged, you’re likely to fail an emissions test. That means that your car is emitting more hydrocarbons than is normal, which is bad for you and the environment. And depending on your area, you may be unable to drive your car until you fix the issue.
Performance issues: A faulty canister filter can affect your car’s fuel vapor management. This can cause a variety of issues, including reduced fuel efficiency, difficulty starting the engine, and a rough idle.
Leaking or collapsed fuel tank: In extreme cases, the fuel tank can actually collapse due to catastrophic EVAP failure. If you notice a whooshing sound when you remove your gas cap, it’s a good indicator that there’s a problem with the vapor venting.
Keep in mind: These issues can indicate other general problems—like a clogged air filter, a bad fuel pump, a damaged intake manifold, or faulty spark plugs—or other EVAP issues, like a malfunctioning control valve.
How often should I replace my evaporative canister filter?
There isn’t a universal replacement interval for evaporative canister filters, although some manufacturers may include this information in the owner’s manual. Instead, you’ll have to keep an eye out for the symptoms of a bad filter, which include a strong fuel smell and a lit check engine light. If you notice these symptoms, it may be time to replace your evaporative canister filter.
Can I replace my evaporative canister filter myself?
Replacing the evaporative canister filter is generally a mid-level job. It requires a moderate level of automotive experience and access to basic tools. While it can make a great DIY project for experienced home mechanics, it may be overwhelming for novices.
If you feel confident in your mechanical abilities and have access to the right tools, you should be fine handling the replacement yourself. But if you’re uncomfortable working on the fuel and emissions systems, you should leave this job for a pro.