I recently started getting an issue with my 2014 Ford fiesta. It has about 112,000 miles. When I put in regular gas it shutters once I turn the vehicle on. The rpms drop from hard then back to normal at times there car would turn off. I read it could be a canister or purge valve. This happens with no check engine light turning on. Also there shuttering stops after I drive for 5-10 min.
I think you are right, something with the evap system. Next time it happens, see if loosening the gas cap has any effect. Don’t drive like that, dangerous, but just as a test. When you fill up the tank, the gas fumes are directed by the evap system into the canister (rather than into the air, to prevent air pollution). The purge valve opens as you are driving the car, to burn those stored fumes in the canister. But it isn’t supposed to open at idle or at slow speeds, only when you are driving at a moderate speed. If it opens when it shouldn’t, this symptom could result. There’s other valves in the evap system that can fail too, like the fuel tank vent valve, etc. But if I had to guess, I’d say your idea is right, the problem is the purge valve or the canister. A shop with the proper scan tool can test the purge valve probably. Problems w/the canister can sometimes be ID’d visually, with the canister on the bench. If the canister gets overly saturated with gasoline (for example if the tank is over-filled), that can break down the carbon beads in the canister, which will then get sucked through the purge valve and clog the injectors sometimes.
The problem might be with the solenoid purge valve.
This valve is normally closed when refueling the vehicle.
If this valve is open, fuel vapors get forced into the engine while refueling.
Then when you go to start the engine, along with fuel vapors that were forced into the engine, the injectors start adding fuel, and you have a flooded condition.
And the engine runs rough.
Tester
What does your owner’s manual require? If it requires hi-test and you’re using regular, try a few tankfuls of hi-test and post back.
The wandering idle after starting, stumbling and dying at times, that straightens out after driving for 5-10 minutes, suggests the possibility of an engine temp sensor problem or even an EGR problem.
If the temp sensor is putting out a bad signal, the ECU won’t know the engine is cold, and it won’t know to bypass the upstream oxygen sensor and run the mix rich while the engine’s cold. Since there’s nothing to compare the temp sensor to, it won’t trip a fault code. The ECU won’t know the temp sensor is bad.
The EGR is my backup guess. If that’s stuck open, metering fuel accurately will be difficult for the ECU to do, since the EGR valve will be letting exhaust gasses be drawn in and displace the necessary oxygen. Once the engine is run for five minutes, the engine will be warm enough for the ECU to again introduce the upstream oxygen sensor into the metering algorithm rather than the “cold engine bypass loop”, and the metering could straighten out and run okay.
I admit, the “after pumping gas” isn’t factored into these guesses, and that would suggest an EVAP problem as others have suggested, but realize that these are additional ideas not intended to displace the EVAP system theories but to add to them. The more different ideas you have is the better your likelihood of finding the root cause.