Bad EVAP Canister Symptoms: Causes and Possible Solutions

Bad EVAP canister symptoms include the check engine light coming on, a subtle hissing sound in the fuel tank, and a strong smell of gasoline in the cabin. The EVAP means the Evaporative Emission Control System, and it controls the gas fumes and prevents leaks.

Bad EVAP Canister Symptoms

The EVAP is highly important in your car as it gives you a perfect emission test and ensures that the gasoline does not evaporate while the engine is running. If you’re wondering what it is like when your EVAP has gone bad, here’s a complete guide below.

A List of the Symptoms of a Bad EVAP Canister 

The EVAP system works by consistently supplying the engine with fuel while preventing vapors from escaping the system. But if the EVAP canister is no longer working, it can lead to poor engine performance and other effects in your car. You should consider the common symptoms explained below if you suspect that your charcoal canister is damaged.

1. Check Engine Light 

Checking Engine Light

Main Sign Engine warning light is on
How to Test Use an OBD 2 scanner 
Possible Cause  EVAP is leaking 
Solution  Clear the code 


The first sign of a bad charcoal canister is the check engine light getting illuminated on your dashboard. Most car owners ignore the check engine light because they’ve been led on by some warnings that can be ignored, especially when driving an older car. Despite this, the warning light might be the fastest way to realize that your EVAP is faulty.

If you notice that the light is on, you can connect the OBD2 scanner to your OBD port, usually located under the dashboard of the driver’s seat. Then, you can run the codes. Once you get a code from the scanner, you should check the meaning. If you have a P0455 or P0456 diagnostic trouble code, it might be because there is a leak in the EVAP system. 

Then, you should inspect your canister to repair the leak or replace the entire canister. You can find it at the back of the vehicle after lifting it up with a jack. You can unscrew the bolts that hold the canister in place, disconnect the wires, and replace the canister. It’s best to ensure you have the same canister as your replacement. 

2. Hissing Sound 

Hissing Sound in Car

Main Sign Loud hissing sound when you open the fuel tank, gust of air
How to Test Inspect the canister
Possible Cause  EVAP system is not purging the vapors, or cracks in the canister
Solution  Replace the canister


Another sign that you should look out for is a hissing sound when you open the fuel tank to refuel your car. Normally, you will hear a slight and subtle hissing sound when you open your gas cap. This is because you have been driving for a long time and so the charcoal canister was unable to make the pressure equal in time. 

But, if you notice that the hissing sound is louder than usual, this is a sign that there is a problem with the EVAP system. In worst cases, the EVAP system won’t be purging enough vapors, causing you to feel a gust of air when you open the fuel tank. In this case, you should replace the canister. 

3. Smoking Exhaust Pipes

Smoking Exhaust Pipes 

Main Sign Visible white smoke from the exhaust pipes
How to Test Check the smoke coming out of the exhaust while driving
Possible Cause  EVAP system is damaged
Solution  Replace the EVAP system 


It’s not common to see puffing white clouds coming out of the exhaust pipe of a modern direct-injection engine. Usually, you see this when you are driving a car with an outdated 2-stroke and carburetor engine. So, if you see that you have a smoking exhaust pipe, especially visible white smoke, there is a problem with the air-fuel mixture.

In most cases, this would be because of a faulty fuel injector or a bad air filter. But it can also be because of the EVAP system. It’s a good idea to check the condition of the system to rule it out from the possible causes. You should contact a mechanic if you are unsure about how it should look or check if you have a failed emissions test

4. Gasoline Smell 

Gasoline Smell in Car

Main Sign Strong gasoline smell in your car
How to Test Inspect the EVAP after smelling the gas
Possible Cause  Faulty EVAP canister
Solution  Replace parts of or the whole canister


If you notice a strong smell of gasoline in your car when you are driving or just standing near your car, there’s a good chance that there is something terribly wrong with your fuel injection system or the EVAP. In cases like this, it’s best to contact a mechanic immediately and keep any flammable objects away from your car since the fuel smell can be ignited.

After checking the fuel injector system and there is no damage to any of the components, the next thing you should do is check the fuel pump. Then, you can check the EVAP for cracks or damage. If you’re handy with tools, you can replace the fuel injector or the EVAP easily. Simply locate it, remove the bolts and connections, and replace it.

5. Refueling Issues

Car Refueling Issues

Main Sign Refueling stops prematurely 
How to Test Check if your car isn’t taking as much fuel as usual
Possible Cause  Clogged EVAP canister 
Solution  Unclog the canister, replace the canister


Another one of the bad EVAP symptoms is refueling issues which an attentive driver will quickly notice. The gas station nozzle is designed to create a strong seal on the fuel tank and pour a large quantity of fuel. So, the charcoal canister will draw the gas out of the tank so that it will fill up with gasoline. This won’t be possible if it is clogged.

With clogged EVAP canisters, the gas or vapors won’t be able to escape. To prevent the vapors from mixing with the gasoline, the system stops the process immediately, even when your gas tank is not full or you haven’t gotten the amount you paid for. If this happens, the best thing is to avoid forcing more fuel in your tank.

You can see a mechanic or clean the canister by yourself. You will need to remove the canister before cleaning, and reinstall it. If it still doesn’t work, you should replace it outrightly. 

6. Rough Idling 

Canister Purge Valve

Main Sign Rough idle, car running inconsistently, car stops randomly
How to Test Inspect the EVAP canister purge valve
Possible Cause  Bad purge valve in the EVAP
Solution  Replace the valve or the entire EVAP


If the purge valve located on the vapor canister is damaged, it can cause a rough idle. You might notice that the car is running inconsistently while driving at low speeds or even when it stops. You should inspect your EVAP canister to check if the purge valve has failed and is sticking open. Rough idling is mostly due to the spark plug so check that first.

If this happens, it will cause a vacuum leak that will affect your engine speed and quality. A vacuum leak can also be due to a damaged or broken purge solenoid or any other hose attached to it. It can cause your engine to stall completely if you don’t check it. So, you should check for damage or a vacuum leak.

7. Low Gas Mileage

Low Gas Mileage 

Main Sign You are using more fuel than usual
How to Test Check your fuel usage
Possible Cause  Bad purge valve
Solution  Replace the purge valve, replace the vacuum hose


You might also notice a poor fuel economy in your car, which is another sign of a damaged canister purge valve in the EVAP. The fuel vapor that your car uses for combustion will get vented through the EVAP system. But with a damaged canister purge valve, the gas will get burned up before it even combusts. This means that you should focus on fuel efficiency.

You should inspect the charcoal canister purge solenoid which makes sure that your car is using its fuel efficiently. If you suspect that this is the problem, you should contact a mechanic to check whether you should replace the vacuum hose or the canister purge solenoid. It won’t be advisable to check them yourself.

8. Difficulty Starting the Car 

Leaking Exhaust Manifold

Main Sign Difficulty starting, engine refuses to start entirely
How to Test Try your engine, check the EVAP canister
Possible Cause  A faulty canister purge solenoid
Solution  Replace the purge solenoid


Another symptom connected to a faulty charcoal canister is the difficulty of starting your car, and this is especially due to a bad canister purge solenoid. The EVAP canister purge solenoid can cause a vacuum leak in your system, and this will make it hard for your vehicle to start.

The vacuum leak will cause unlimited, outside air to get into the engine, and this will cause the air-fuel ratio to become unbalanced. By interrupting the internal combustion process, the engine might be hard to start or it will refuse to start at all in the worst cases. 

9. Weak Engine Performance

Weak Engine Performance 

Main Sign Weak acceleration, rough idle
How to Test Inspect the EVAP canister
Possible Cause  Failing purge vent valve
Solution  Replace the canister purge valve


A vehicle with a failing EVAP purge valve will also deal with poor vehicle performance. When driving your car, it will feel like it is not giving out enough power for acceleration and it will be driving weakly instead.

Also, if you press the pedal down, you will find yourself moving slower rather than faster. The failing EVAP canister purge valve will lead to slow acceleration and so it needs to be repaired or replaced right away. 


With our guide on the bad EVAP canister symptoms, you can identify them and replace the canister yourself or contact a mechanic.

Here’s a summary of the main symptoms before you go:

  • The check engine light is on and when you check the code, it says P0455 or P0456, which are signs of an EVAP leak.
  • There is a loud hissing sound and a gust of wind when you open the fuel tank, and this is because of a faulty or cracked EVAP system.
  • There is a smoking white cloud coming out from the exhaust pipe which can be because of a damaged EVAP system that needs to be replaced.

It’s important to note that it is relatively easy for you to replace your EVAP system without a mechanic, but that’s only if you’re good with DIY repair. You should contact a mechanic with an affordable canister replacement cost if you are unsure. 


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