The vapor canister purge valve is an important component of the EVAP or evaporative emission control system of a car. It is the one that stops the fuel vapors that are created in your gas tank from getting out by confining them temporarily in the charcoal canister. These fuel vapors will be removed from the canister and will be burned inside the engine when it is running. But just like any other parts of a car, the vapor canister purge valve is also susceptible to wear and tear and other problems. It can weaken or become obstructed. A bad vapor canister purge can have symptoms like an illuminating check engine light, rough idling, hard starting, and a decreased fuel economy.
Vapor Canister Purge Valve: What does a Vapor Canister Purge Valve Do?
Like mentioned earlier, the vapor canister is a vital part of the car’s evaporative emission control system. You need to understand that the EVAP system paired with a vapor canister purge valve control is very important since the emissions from the car are harmful to the environment. This is because aside from the toxic fumes coming out from the tailpipe, there are other ways a car with an internal combustion engine can be harmful to the environment. The gas that we put in our cars can evaporate and it can pollute the air which can cause respiratory problems when inhaled.
These vapors of gas or diesel created inside the gas tank are what the vapor canister purge valve regulates. Its task is to restrict these vapors from escaping from the gas tank. It traps the gas vapors from the gas tank and temporarily stores them in the charcoal canister just until the engine is running under certain conditions since the canister can only hold so much gas vapor. These trapped gas vapors will be purged from the canister and will be burned inside the engine. The vapor canister purge valve does this and it is also the one that accurately controls the amount of gas vapor that will be removed from the gas canister.
The vapor canister purge valve is basically the component that opens and closes the passage between the vapor lines coming from the gas tank and the intake manifold. It acts like a switch that when it opens, the air intake will be injected with the gas vapors and when it closes, it stops.
In newer cars, the vapor canister purge valve is a solenoid that is electrically operated and is controlled by the engine computer. It means that when the engine is off, the purge valve is closed and when the engine is running, the engine computer slowly opens the vapor canister purge valve to let a certain amount of gas vapors out to be moved from the canister and be burned in the engine.
It means that when there is no electricity supplied to the solenoid, the valve stays closed and when a voltage is applied, it opens up, enabling the purge valve to release the gas vapors into the engine. If the solenoid has some issues and fails to function properly, it won’t be able to open or close, which can result in many problems.
Many modern cars have power control modules or PCM that only enables the gas vapors to be released when the car is running at a steady speed, mostly when it is driving on higher gears. This is because when the gas vapors are released when the car is driving at low speed or when it is under load, it can alter the air to fuel ratio that can cause the engine to experience misfires.
Vapor Canister Purge Valve: What Happens When a Vapor Canister Goes Bad?
We now understand what a vapor canister purge valve does and why it is important. Our vehicle needs a vapor canister purge valve that is working properly so it won’t release any gas vapor in the environment. It needs to be able to seal correctly.
However, the vapor canister purge valves are susceptible to damages, especially the ones in the older cars. It is said that the older the car is, the less reliable its vapor canister purge valve is. This is because the automakers had to make the design quickly and build an emission system that can meet the new clean air regulations.
Sometimes, the problem lies in the materials that the vapor canister purge valve is made of. It is usually made with cheap plastic and it can suffer wear and tear as the car ages. Its one side is connected to the charcoal canister and the other end lets gas vapor to flow to the intake manifold.
When the vapor canister purge valve becomes weakened, it can cause a vacuum leak. When this happens, it will have a direct effect on the engine idle speed and quality. The vapor canister purge valve can also malfunction and stick open or closed or maybe get obstructed that can cause the gas vapors to not be released.
There are also instances where the gas vapors are released but at an incorrect time. This can cause an incorrect air to fuel ratio which can cause a number of issues. The vapor canister purge valve should always open and close at the right time to regulate the proper flow of the gas vapors.
For the modern cars that are equipped with a solenoid that controls most of the purge valves, the solenoid can also malfunction over time, causing the vapor canister purge valve emission system to stop working. When the vapor canister control solenoid malfunctions, it can trigger different trouble codes that can be a hassle to diagnose and repair.
The trouble codes that can be triggered by a bad vapor canister purge valve include P0440 or Evaporative Emission Control System Malfunction, P0441 or Evaporative Emission Control System Incorrect Purge Flow, P0443 or Evaporative Emission Control System Purge Control Valve Circuit, P0444 or Evaporative Emission Control System Purge Control Valve Circuit Open, and P0445 or Evaporative Emission Control System Purge Control Valve Circuit Shorted.
Vapor Canister Purge Valve: What are the Symptoms of a Bad Vapor Canister Purge Valve?
A faulty vapor canister purge valve can cause a lot of problems. It is for this reason that you need to know its common symptoms so you can detect it early and have it repaired immediately. Here are some of the symptoms of a bad vapor canister purge valve:
- Check engine light.
Like mentioned earlier, a bad vapor canister purge valve can set off some trouble codes that can trigger the check engine light to illuminate. This can happen when the sensors are not receiving any signals coming from the purge valve. The sensors will then send this information to the car’s computer which will set off the check engine light to alert the driver that there is a problem.
Although there might be many other possible reasons why your check engine light came on, a faulty vapor canister purge can be one of them since it is directly related to the proper functioning of the car’s motor. To cross out any other possibility, you need to have it checked by a mechanic to get a proper diagnosis.
- Hard starting.
A faulty vapor canister purge valve that has caused a vacuum leak can result in hard starting. If you notice that you have trouble starting your car, it can be an indication that your purge valve is damaged or is leaking. This is because it can no longer prevent the outside air from getting into the engine. This unmetered air from the outside can mix with the fuel in the cylinder chamber, which can lead to issues with the air to fuel ratio. When this happens, the performance of the car will be affected and engine problems can occur, including hard starting.
- Rough idling.
Problems with the vapor canister purge valve or charcoal canister can cause a vehicle to idle at a lower RPM than usual. It is commonly known as rough idle. Rough idling happens when the car is not running smoothly. It might run but at an inconsistent rate, more so when you are stuck in a traffic idling. If the RPM gets too low, it can cause the car to shake or the engine to die.
Rough idling can happen when there is a vacuum leak developed because of a faulty purge valve or canister. A damaged solenoid valve and any hoses connected to it can also cause this problem to occur. The moment that you notice this problem, it is best that you have it checked and repaired as soon as possible since a vacuum leak can greatly affect the engine idle’s quality and speed.
- Poor fuel economy.
A vapor canister purge valve that does not open or close as it's supposed to can cause a decreased fuel economy. When it is malfunctioning, it can lead to gas vapors that are used in the combustion to escape and be vented out to the environment. Since that gas vapor is supposed to be used to burn in the engine, the car will now have to use more fuel to make the same amount of power, causing an increased fuel consumption.
- Failing emission tests.
The vapor canister purge valve is a vital component of the vehicle’s EVAP system. It can help prevent the toxic vapors or fumes from being emitted from your car. The purge valve’s task is to redirect the gas vapor back into the engine, keeping the harmful hydrocarbons from being released to the atmosphere.
When the purge valve malfunctions or fails, it will no longer be capable of redirecting the gas vapors and keep them from escaping from your car. Remember that a faulty vapor canister purge valve can also cause an incorrect air to fuel mixture that can lead to creating more CO2 and hydrocarbons. So, if you fail your emission tests, it can be an indication that you have a faulty vapor canister purge valve. Have it checked by a mechanic right away and have it repaired or replaced.
Vapor Canister Purge Valve: Can You Drive with a Bad Canister Purge Valve?
A faulty vapor canister purge valve might not be as urgent as the problems on the car’s other components but it does not mean that you can ignore it and just continue driving your car. Although you can still drive a car with a bad purge valve, the experts are not recommending it.
When you still drive your car knowing that there is a problem with your vapor canister purge valve, you are risking damaging your car’s evaporative emission control system and its other components. Plus, you will be driving with a car that consumes more fuel and emits more harmful emissions than necessary. It is best that you fix the problem the moment you notice any symptoms of a failing vapor canister purge valve.
Vapor Canister Purge Valve: How Much Does it Cost to Fix a Purge Valve?
To fix a damaged vapor canister purge valve, it can cost you around $100 to $230. Most of the repair cost usually covers the needed parts since the amount of time the mechanic needs to fix or replace it is not that long. It only requires a simple fix and if you want to save a few bucks, you can choose to have it repaired in a local auto shop instead of going to the dealership.
But if you know your way around cars and are confident working under the hood with all the different kinds of harnesses and wirings, you can choose to fix it yourself since it does not require much in-depth work. You just have to be familiar with how an OBD-II scanner works or how to use it.
The vapor canister purge valve, together with the car’s EVAP system make sure that lesser harmful emissions from the car are released into the environment. If you notice any signs of a faulty vapor canister purge valve, it is important that you have it checked and repaired immediately not just to keep your vehicle in good shape but to help the environment as well.