Symptoms of a Faulty or Faulty Canister Purge Solenoid

Common signs of a problem with a vehicle's EVAP canister purge solenoid include rough idle, difficulty starting, and a check engine light coming on.

The canister purge solenoid is an emission control component that is commonly used in the fuel vapor emission control (EVAP) system of many modern vehicles. Modern vehicles are equipped with an EVAP system that works to reduce evaporative emissions that can come from the vehicle's fuel tank being emitted as fumes. The EVAP system captures this vapor in the charcoal canister and recycles it to use as fuel for the engine and prevent pollution.

The canister purge solenoid, also called the EVAP canister valve, is responsible for "purge" of the EVAP system by acting as a switch that allows vapors to enter the engine. When the purge solenoid fails, it will cause problems in the EVAP system, which will affect the vehicle's emissions. Typically, a failed purge solenoid exhibits any of the following 5 symptoms that may alert the driver to a potential problem requiring service.

1. Rough idle

One of the first symptoms of a bad canister purge valve is rough idle. In this case, you will notice that the vehicle is unstable while stopped or driving at low speed. If the canister purge valve fails and sticks open, it will create a vacuum leak that can affect the speed and quality of the engine at idle. A vacuum leak can also be caused by a broken or damaged purge solenoid or any of the hoses attached to it. This needs to be resolved as soon as possible, as it can lead to a complete engine stop.

2. Poor engine performance.

In addition to a rough idle, a vehicle with a bad EVAP canister purge valve will show signs of poor engine performance. It may seem that the engine is running “weakly” and is not producing enough power to accelerate. When accelerating, you will feel that you are pressing on the pedal and moving more slowly. A disrupted combustion process caused by a faulty purge solenoid will result in slow acceleration that must be repaired immediately.

3. Difficult start

Another symptom commonly associated with a bad canister purge solenoid is difficult vehicle starting. Again, if the vacuum leak is the result of some sort of problem with the canister purge solenoid, it can cause issues with reliable starting of the vehicle. A vacuum leak will introduce unmetered outside air into the engine, which can disrupt the air-fuel ratio and cause performance problems due to the interruption of the internal combustion process. Eventually, the engine may refuse to start at all.

4. The Check Engine light comes on

A bad canister purge solenoid can also cause the Check Engine light to come on. If the computer detects any problem with the purge solenoid circuit or signal, it will turn on the Check Engine light to alert the driver that there is a problem. The Check Engine light can also be caused by a variety of other issues, so it's a good idea to scan your car for trouble codes to be sure.

5. Low fuel economy

Low gas mileage is another sign of a bad canister purge valve. The fuel vapors your car would normally use for combustion are instead expelled through the EVAP canister. Instead of entering the combustion chamber, the gasoline is burned before it enters the combustion process. This means that your car will not use fuel efficiently and instead waste it.

The canister purge solenoid is an emission component and therefore an important element in ensuring that a vehicle meets emission requirements. The purge valve prevents toxic hydrocarbons in the fuel from leaking out of the exhaust pipe. For this reason, if you suspect that your canister purge solenoid may have a problem, contact a professional vehicle diagnostic technician to determine if the canister purge solenoid or vacuum hose needs to be replaced.