I have a problem starting my car only after filling it with gas. All other times it starts normally. The GM dealer mechanics seem to be stumped with the issue. When I put gas in my car and then try to start it, i have to do the following routine. I try to start it and it stalls the first time. I then need to pump the gas while trying to start it a 2nd time. It usually starts the 2nd time, but I need to keep revving the engine for a minute or else it stalls again. One the rpm’s stabilize around 10, then it’s ok to drive. After this initial routine, all the other times i start the car are normal until the next time I put gas in it.
A second possibly related issue happens sometimes after driving on the highway. When I pull off the highway and stop at a stop light, the car sometimes seems to hiccup and then stall. It usually starts up right away and that’s the end of it. Any ideas?
The first issue related to fueling up sounds like an evaporative emissions system problem. This is the system that contains and controls the gas fumes from your gas tank. The fumes run through a system of hoses to a charcoal canister where they are stored and occasionally purged into the intake where they are burned. The key to the system is that it’s only supposed to contain gas fumes. But there is a vent on top of the tank where the fumes go. When its working only fumes are able to go into the evap system. When leaky it will allow liquid gasoline in and then your engine ends up flooded on restart. Are you in the habit of “topping off” your gas tank (i.e. you keep pumping for a few clicks after the first click-off of the pump)? If so then you may have messed up that valve. Either way, try a few fill ups where you don’t completely fill up. Got to 3/4 or 7/8 tank of so and stop filling. See if that matters.
The second issue sounds like a sluggish idle air control valve (IACV) though it could also be form other things. Most often an IACV is easy to remove and clean.
As @cigroller said, don’t top off. You could replace the evap canister and it would probably fix you fill up problem. IAC clean will fix the other.