I have a 98 Ford Expedition, shut off on its own while driving down highway after check engine light started blinking, started back up right after. Got home, Coolant smells like gasoline. What could be the problem?

Perhaps a blown head gasket. It takes a fairly good misfire for Fords computer to actually flash a code. A blinking check engine light indicates a cylinder or multiple cylinder misfire. The fact that you smell gasoline in the coolant AND your check engine light is flashing leans toward a blown head gasket. I'll explain: When a head gasket blows between a cylinder and a coolant jacket (port coolant runs through to keep engine cool) that coolant can now enter into the cylinder chamber and the fuel and exhaust can also enter into the coolant system.Your coolant system can be pressurized up to 16psi under normal driving conditions so there is quite a force there and if there is a place for that coolant to go, it will find it. When coolant enters into the cylinder it creates a misfire. (water mixed with fuel and air does not make a very good ignition source) So then on the exhaust stroke, it can then expel this fuel/water mix back into the coolant system by way of that blown gasket, during an exhaust stroke the pressure is well beyond the 16lbs of your coolant system and can then force its way back in. This would explain a flashing light and the smell of fuel in the coolant. But for it to die while driving down the road....it would have to be misfiring on more than just 1 cylinder or there is a separate issue on that one all together. With a head gasket blown between the coolant port and the cylinder, you may not see a visible leak from the outside. In this situation one would look at the coolant for signs of floating oil or carbon, pull the oil dipstick and look to see if it is a milky brown color, bubbles also indicates water and/or use a chemical test. You can't pick that up at walmart though. But this chemical test would be a blue chemical placed into a clear cylinder or tube with a suction ball at one end. You remove the radiator cap, start the vehicle then place this tube over the spot where the cap was. Must not let it make contact with the coolant though. Squeeze the ball several times, this draws in air and/or vapors. IF the blue chemical begins to turn yellow it has detected exhaust gases in your coolant system confirming a blown head gasket. Sorry so lengthy...hope it helps.