Does the check engine light in your car illuminate sometimes, with no other apparent symptoms being present? And in certain situations, even the engine may run rough while idling. Problems with the EVAP system are among potential issues that would cause such behavior. Having only several parts and components, this is a simple system that requires no maintenance. Because of this, many drivers are not aware of its existence, not to mention recognizing the symptoms. In this article, we will explain what is the EVAP system and how to spot any potential issues with it.  

What does the EVAP system do?

EVAP is a general abbreviation for Evaporative Emission Control System. This is an enclosed and sealed structure, which contains fuel vapors and stops them from escaping into the atmosphere. However, having a sealed gas tank is potentially dangerous, because fuel vapors would cause a significant pressure increase in it. To avoid this, the EVAP system uses a series of hoses and valves that feed these vapors into the intake manifold. There is also a charcoal canister in between, whose task is to purge the vapor before it enters the engine. This makes the vehicle more eco-friendly and less damaging to the environment.

How to tell if there is an issue with it?

Being under control of the on-board computer, any issue within the EVAP system will trigger a Check Engine Light (CEL). Just like in any other case, this will generate a corresponding error code that might help track down the problem. This may be something as simple as a loose gas cap, especially if this happened just after filling up the tank. Both purge and vent valve, whose function is to control the vapor flow, can get stuck or faulty. And the most common failure points are the vapor lines, which crack or break if brittle. Sometimes the resulting leak is large enough to affect the engine performance while idling.

Can I repair the EVAP systems myself?

Despite its simplicity, tracking down the issues within the EVAP system can be quite challenging. This is especially true with small cracks somewhere on the vapor lines that connect the fuel tank to the engine. Sometimes, discovering them is only possible by using a special smoke generating machine. Vent or purge valves are quite easy to diagnose if faulty by checking stored codes with a scan tool. However, access to these valves can be difficult in some cars because of the limited space inside the engine bay.

How important is this service?

As we show in this article, the EVAP system is quite simple and straightforward. Still, tracking down any issues with it can be difficult, as it may require specialized equipment and experience. If you don’t have the right tools or don’t feel up to the job, consider hiring a professional. At FixMyCar, we have certified and seasoned technicians that can come to your home and solve all EVAP system related issues. This will ensure that all important components are checked and your car is ready to hit the road.