Q: Emissions system

asked by on

Purge valve was replaced last week and engine light came back on 4 days later. Mechanics at shop say now I need a new gas cap. Is This coincidental that both stopped working at same time? It feels like I paid $170 last week was for nothing especially if it's just needed a gas cap. Thoughts please and recommendations

My car has 64000 miles.
My car has an automatic transmission.

This is not coincidental as the purge valve and the gas cap, among other parts work together to keep your fuel evaporative emissions system in check. The EVAP system prevents fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system collects and temporarily stores the fuel vapors in the charcoal canister. The charcoal canister is filled with activated carbon pellets that can absorb the fuel vapors. When the engine is running, the fuel vapors are purged from the canister and burned in the engine.

The vent control valve (solenoid) controls the flow of outside air in and out of the charcoal canister. One side of the vent valve is connected to the charcoal canister. The other side is connected to the vent hose that has a filter or screen at the end and is attached to the car body or frame. In some cars, the vent valve is attached to the canister. In others, it’s installed separately near the canister. The vent valve is controlled by the engine computer (PCM). Normally the vent valve is open. It closes when the engine computer tests the EVAP system for leaks. If a leak in the EVAP system is detected, the Check Engine light will illuminate on the dash and the trouble code related to the problem will be stored in the engine computer.

When an air leak is present in the EVAP system, the MAP sensor will not be able to determine the air density, and the MAF sensor will not be able to determine the volume of air, entering the engine correctly. This will lead to an over fueling situation or an under fueling situation depending on the size of the air leak and engine operating speeds and load. This may eventually lead to catalytic converter problems as well as misfiring problems. I would recommend having an expert from Your Mechanic come to your home to take a look at your car to diagnose your EVAP purge solenoid.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Emissions system

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I have a 2009 Jetta Sportswagen TDI that shakes bad between 40 and 50 and tires and wheels are okay.

Hi Kris. Thanks for contacting us tonight. Vibrations like you've described can be very confusing to diagnose. Even tire "experts" occasionally get this one wrong (as they assume that if the tire balance is good - it shouldn't be the...

Q: My emergency brake can be pulled without having to push the button

Hi, thanks for writing in. Have a technician check the emergency brake ratchet mechanism in the handle for any problems like a broken spring or ratchet gear. Also have them check the emergency brake cables for proper tension. It may...

Q: Hunting idle speed and stalling.

Hi There, It sounds like you may have an issue with your evaporative emissions control system causing the hunting idle problem and the no start issue after filling up your fuel tank. Your car has a small purge valve called...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.