818 loss of power with full fuel tank

[autostang]

I have an issue where the car will lose power briefly (engine sort of misses, then keeps going) after I have completely filled the gas tank. After a full fill up it happens every few miles and the frequency decreases as I use gas. After ~3 gallons have been used I don't have the issue at all and the car runs great. My typical fix is to just never fill the car all the way up, but I am curious if there are thoughts as to what is happening? It would be nice to be able to just fill it up. I have a vent tying the top of the tank into the fill neck.

[idf]

With the tank vented to the fill tube you have a closed system, ie the tank isn't actually vented to atmosphere. The fuel the pump is trying to pull from the tank can't be replaced by air, except slowly through some small leaks. When the fuel level has dropped perhaps there is enough compliance in the air now in the tank for the pump to draw against it. Try disconnecting the vent from the filler and see if the problem goes away.

[autostang]

I do still have the normal vent line hooked up through a charcoal canister and purge valve. I added a second vent just to help with filling the tank. Something along the lines of what you described does make sense though.

[idf]

I wonder if there is a restriction in the evap system that is preventing air from entering the tank fast enough. Disconnecting either the evap or vent, or running with the gas cap off, might give you a clue as to whether this is the right direction to pursue.