Escort skips/misses after fillup

[Seneca_Tiger]

My mother-in-law has a 1994 Escort w/ the 1.9L 4-cylinder engine that is doing something really weird. Right after the car is filled up with gas, it starts to miss and skip. Once it burns some off it runs better. I was thinking it may be something in the evap system (not letting enough air get into the tank to displace the fuel that is burned off) but why would that get better as fuel is burned off? Am I way off base here?

[denisond3]

I dont have an answer - just a further thought. With our Escort, the gas station is about the only place we ever start the car up when its only been shut off for less than 10 minutes. All the rest of the time the engine has had time to cool for a while before we restart it. So maybe it is related to the engine/computer/sensors being fully warm?

Does it happen if the tank is not filled to full - such as filling it only to 3/4ths?

Right after fill up is the only time the fuel flowing back to the tank from the fuel pressure regulator would be likely to encounter resistance to its return, from a full fuel tank. Maybe the pressure regulator is not regulating to the same pressure as a result. This would be likely to result in running rich - though not necessarily enough to cause any black smoke from the tail pipe.

P.S. We have a Dodge minivan whose vapor purging cannister isnt working right. We get too much fuel vapor pressure in the tank as a result. The short term was to leave the fuel cap loosened till than tank ws below 3/4ths full. I know that will cause a "Service Engine" light in new cars, but not in the older minivan.

[Seneca_Tiger]

That is an interesting theory. I read a story like that about a guy who's car would vapor lock if he bought vanilla ice cream - if he bought some other flavor the car ran normally. Turned out the car was vapor locking and the other flavors took longer to get, so the vapor lock would be gone by then. I'll have to check into that one.