Hyundai Repair: Car Problems, fuel vapors, charcoal canister

Question
My car seems to sputter after i put gas in it. Its a 2004 Hyundai Accent GL. This started about 3-4 weeks ago and also rarely occurs when i start the ignition. It also does the same thing when I shift the gears from park to either reverse or drive, usually after pumping gas, but also occasionally when starting ignition. Any idea on what the problem might be, how to fix it and how much it might cost? My car is still under warrenty for a couple thousand more km, although I taken it in a couple times and had to pay out of pocket both times. Any suggestions?

Answer
Your purge control valve is stuck open.  This is pretty much the only possible problem that would cause driveability problems only after refueling (unless you overfill the tank).  It's also consistent with long cranking times and stalling after the car sits for a significant period of time.

The function of the purge control valve is to meter excess fuel vapors from the charcoal canister into the engine to be burned off.  If the valve sticks open, there will be a large amount of fuel vapors pushed into the engine when they're displaced by gasoline from fueling the vehicle.  This causes the engine to be flooded.  Similarly, as the vehicle sits, more and more fuel vapaors can accumulate in the intake manifold, causing a similar flooding condition.  This should be covered by your factory warranty.