The Evaporative Emission Control (EVAP) system features a vapor canister purge valve which manages the quantity of fuel vapor coming out of the charcoal canister.
The purge valve and charcoal canister work together to recycle the emissions back into the engine so that they’re eliminated as the internal combustion process takes place.
But what if the purge valve isn’t doing its job? Let’s look at the most common symptoms of a bad EVAP purge valve and how much it’s going to cost to replace if it fails.
What is a Vapor Canister Purge Valve?
A vapor canister purge valve is a component of the evaporative emission control system and its main function is to bring those stored vapors into the engine from the charcoal canister.
There is a vacuum line that connects the intake manifold with the charcoal canister that contains the fuel vapors. The purge valve lies within the vacuum line to allow these vapors into the intake manifold at the appropriate time.
Older vehicles use vacuum operated purge valves while newer vehicles used electronically operated ones.
How Does a Vapor Canister Purge Valve Work?
When the purge valve opens, the fuel vapors can access the intake manifold. From there, the vapors are sent into the internal combustion chamber where they will be ignited with the fuel and air mixture.
If you have an electronic purge valve, then the engine control unit manages it. This is the central computer of the vehicle which will calculate the exact amount of vapor that needs to go into the engine.
Once it allows enough vapor through, the purge valve will close so that no mater vapor gets through. The vapor will just sit in the charcoal canister until it is needed again.
Bad Vapor Canister Purge Valve Symptoms
If you have a bad vapor canister purge valve, the symptoms that you experience will potentially be worse than the symptoms of a bad charcoal canister. You need to understand what these symptoms are if you are going to tell the difference between the two possible problems.
Here are five things to look out for:
1) Check Engine Light
There are dozens of reasons for the Check Engine Light to illuminate on your dashboard. If you have a damaged or worn out purge valve, this could possibly cause the Check Engine light to come on.
There are sensors which detect when the purge valve is working. But if there are no signals coming from the purge valve anymore, this will indicate to the sensors that the valve must be damaged.
The sensors will then relay this information back to the engine control unit, which will result in the Check Engine warning being given to you.
2) Rough Idle
If your car engine has a rough idle, then it is no longer running smoothly. It will run at an inconsistent rate as you’re driving, especially when stopped at a stop sign or red light.
The longer you continue to let this problem persist, the more consistently your engine will run. The worst point will be when your engine stalls altogether.
Try not to let it get this out of hand. Usually, when the purge valve is to blame for the rough idle, it will cause a vacuum leak which will impact the idle speed.
3) Trouble Starting Car
If you have a vacuum leak that was brought on by a bad vapor canister purge valve, then you will probably have difficulties starting your vehicle. This will cause outside air to uncontrollable enter your engine and interfere with the overall internal combustion process.
If you have unmetered air mixing with fuel in the cylinder chamber, then it will cause engine problems for sure. The most obvious problem will be an engine that does not start.
4) Poor Engine Performance
If you are able to start your vehicle with a bad vapor canister purge valve, don’t expect it to be a smooth ride. You will almost certainly experience weaker performance from your engine.
In other words, your engine won’t be able to generate as much power to provide the acceleration that you are demanding as you press down on the gas pedal. This will be most obvious when going uphill or attempting to pass another vehicle.
5) Emissions Test Failure
As you know by now, the vapor canister purge valve is responsible for redirecting fuel vapors back into the engine. This is preventing toxic hydrocarbons from being emitted from your tailpipe.
So, if you were to have a failing purge valve, then it wouldn’t be able to redirect those fuel vapors and prevent them from escaping your vehicle. You will find this out the hard way when you go for your emissions test and end up failing.
If this happens, have the mechanic check your purge valve to see if it’s the part responsible for the failed emissions test. If it is worn or damaged, then you will need to replace it promptly. Then you should be able to pass the emissions test.
Vapor Canister Purge Valve Replacement Cost
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The replacement cost of a vapor canister purge valve will be somewhere between $130 to $230 on average. The main expense will be for the part itself, which should cost around $75 to $120.
The amount of time a mechanic needs for replacement isn’t too long, so you are only looking at around $50 to $100 for the labor cost. It’s best to skip the dealership service area for a simple task like this.
You’ll save yourself a lot of money by going to an independent auto repair shop or simply do the replacement yourself if you have even a little bit of auto repair or maintenance experience.
Causes of EVAP Purge Valve Failure
A vapor canister purge valve can fail for several reasons:
- Dirt and Debris. The most common cause of failure is contamination from dirt, dust, or other foreign materials that can interfere with the valve’s ability to open and close properly.
- Mechanical Failure. Like many other mechanical components, the purge valve contains moving parts that can wear out or break over time, leading to a failure.
- Electrical Issues. The purge valve is controlled by the vehicle’s computer and requires electrical activation to operate. Faulty wiring or solenoids can prevent the valve from functioning.
- Overfilling the Fuel Tank. Overfilling can force liquid fuel into the EVAP system, potentially damaging the purge valve and other components.
- Aged Components. Rubber seals and hoses connected to the purge valve can deteriorate with age, leading to leaks and valve failure.
- Faulty Sensors. If sensors that provide data to the EVAP system malfunction, they can cause the purge valve to operate incorrectly.
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my van starts right up when cold but if i turn it off it wont start i have to push the gas pedal all the way down for it to start again help
I’m having trouble everytime I try and get gas. It will only let me put a little in sometimes $1.68. and the gas pump will shut off and won’t let me pump anymore. My Mechanic said it’s the purge solenoid. The car runs fine starts fine and no engine lite is on. Is that the problem.
I would trust your mechanic here. Problems with the evap system can lead to the pump shutting off due to back pressure in the system as you add more fuel.
Honda civic 2012 bad starting when car stop more than 6 hours
But after bad starting the car start good and no problem
Does the car crank for a long time or crank slowly?
2007 Honda Accord cranks but wont start after running out of gas, refueling. Lately has been hard starting after refueling but this time it won’t kick over at all. Had it towed home and now I’m getting codes for misfires on multiple cylinders and also getting P0496 evaporative emission high purge flow. So I think the purge valve may be stuck open and needing replacement but my question is would the valve being stuck cause my engine not to start at all ?
I have a Cadillac CTS 2005 V6 when the car cranks from a cold start runs great idles great those 20 30 minute drive just fine what has been noticed and is consistent what you drive about an hour to an hour and a half the engine completely starts losing power on the highway you can’t get past 60 miles an hour and when you press the gas it decelerates so you barely put your foot on the gas and as five-minute intervals go by you start losing about 10 miles an hour every 5 minutes until eventually won’t go over 20 30 miles an hour in his running terrible once the car cools down completely for a couple hours it cranks up and is good to go again until another long drive it does it again I was told they Pearl up and loosen the gas cap with no help brand fuel cleaners but one thing I know is it is very consistent to the fact it does not do it until the car is running for at least an hour to an hour and a half and once it starts the car has to be completely cool down one strange thing it does do though we filled the car all the way up then after about an hour to an hour and a half it starts failing it’s on about 3/4 of a tank pull to a gas station with the car running terrible fill it back up and the car runs good for about another 30 minutes I’m stumped at this point I can’t get a good 100% correct answer
Check your fuel system and catalytic converter. I wonder if the cat is clogged. When was the last time the fuel filter was replaced?
Something definetly in the fuel system, after it’s been running a while and then the problem starts…If I add fuel it then will start running good again for a period of time until it then starts again….Once the car cools for atleast a couple hours it will then run it’s best until
this starts again..?????????????
Why would adding gas allow it to run good again?????
Sounds like fuel pump
I have a Toyota Echo and in the morning, when starting the vehicle, I smell fuel odor coming out the tail.
Is the charcoal vapor canister saturated and what type of activated carbon can use for refill, as well filter material?
Vehicles often run rich on startup and this in itself is no cause for concern; they are programmed this way intentionally. Do you have any other symptoms or stored codes that made you suspect there is a problem?
I have a 2013 corolla with 10.3 volts at the evap control valve. It takes 12 volts to open it. How do I correct this problem? Thanks Dave
Check your ground straps, make sure they are clean and tight. Then check the wiring leading up to the evap control valve to make sure you don’t see any issues like broken insulation.
thank you for your help it was needed thank you
May also be fuel or tuning to fuel grade Have not tried 91 as run on 95
2018 Mitsubishi ASX purge valve knocking on idle only when hot.
Appears to be due to being mounted on firewall.
Anyone else experiencing this.
Reruns quiet when cold. Varying levels of knock at idle.
Are there any design changes?
Appears to be design fault as not necessary to be on firewall.
Yes I have exactly same problem.
I have the same problem on my 2017 asx only when hot the ticking. I’m going to change the canister purge valve solenoid
Will a bad purge valve or canister make the fuel pump go bad I’m on my 5th one?
I suspect you have a different issue. Do some testing of the fuel system to determine the root cause.
According to some mechanics, tank mounted fuel pumps are kept cool from the movement of fuel over it. If you habitually keep the tank below 1/4 or 1/8 of a tank, it is possible for the fuel pump to not have fuel covering the pump at all times which can allow the pump to run too hot.
Yes, this is true.
Might have to drop the tank and mop it out
I have 2006 Dodge Ram 1500. Replaced fuel pump and fuel filter. Engine light came back on. Not reading any leaks (which it did before, we fixed 5 leaks) and not reading gas cap, which it did before, too. So, leads me to believe the fuel canister and/or the purge valve, since they work hand in hand. Will replace that and go from there. Good luck !
Replaced purge valve. And still shows same code and wont pass inspection. Replaced it last ur and it passed. Now same thing again. But check engine light back on. What could code reader not be telling me?
It killed another one, check the Thermister, check for cracked vacuum line hoses
also check for cracked hose
Will a bad purge valve or canister cause the RPM’s to go up higher than normal? I have a 2014 Toyota Venza and there’s no check engine light, but the dealership said I need a new canister. They also wanted to charge almost $700 for the repair. 🙄