I have a 2019 Toyota Highlander Hybrid with 4000 miles that one morning this week had an engine sputter (as if the engine was missing somewhat) immediately after starting and 20 minutes of driving later had the Check Engine light go off. I checked the gas cap and it was fine, so I took it to the dealer as instructed; during the 30 minute drive to the dealer the engine ran fine. The dealer tells me that there is gasoline in the charcoal canister and it must be due to my overfilling the gas tank and thus is not covered by warranty. I never top-off the tank and the last time I filled up the car with gas was two days previously, after which I drove it for 30+ minutes home and had no problems. The issue started two days later first thing in the morning.
Is it a reasonable story that without topping off the tank, I somehow overfilled the tank to the point that it flooded the charcoal canister? Or is there another potential explanation? Could the overfill check valve potentially play any role - or anything else? Thanks to all for your help and thoughts.