Engine runs rough?

1998 Ford F-150 mileage: 78,786. My truck is an extended cab pick up truck, cruise, automatic transmission, power steering, power brakes (ABS in front). When the weather got cold here in Wisconsin, the truck started running rough when it first was started, but then smoothed out as it warmed up. This became more prevalent below ten degrees F. I knew the truck was due for a tune up and took it in. The garage told me that my spark plug wires were bad, probably original equipment, and they replaced the wires, plugs, cap, and rotor. Two days after I got it back, I had the same rough running problem when I started it and as I listened to it it seemed that the problems were similar to the choke sticking on an older carburetor type fuel system. I called the garage and made an appointment, but was not able to get the truck in before it quit running. We got a cold snap, I went out to start the truck, and it ran very rough for a short time and then quit. I tried several times over the next two days to start it, but it would not start. It would turn over fine, and it would try to fire, but just wouldn't go. It emitted a strong smell of raw gasoline and I had it towed to the garage. The garage had the truck for three days and called me up to tell me that they could find nothing wrong with it except that it was badly flooded. They told me they had to take the plugs out and dry them off and they had to change the oil. There was less then five hundred miles on the oil change. The mechanic stated that there was an extra quart of fluid in the crankcase and a strong smell of gas. He said that after he changed the oil they put the truck on a diagnostic computer and they could find nothing wrong except that the computer found gas fumes still present in the crankcase. I got the truck back last week and used it to drive to work on Friday and Saturday. Both days it still had symptoms of running rough when it was cold but would smooth out as it warmed up. Saturday I filled it with gas and my wife and I went out for dinner. The round trip to the restaurant was about twenty eight miles. The truck again ran rough until it warmed up, and seemed sluggish at city driving speed. The truck used a quarter tank of gas on the twenty eight mile trip. Can you tell me what might be wrong?

Your fuel pressure regulator is probably failing causing excessively high fuel pressure, which causes your engine to flood. This of course would result in extremely poor gas mileage.

This is my Dad's truck. It started running rough a couple weeks ago and has gotten worse. Replaced inline fuel filter, no help. Replaced both front OS2 sensors, no help. Mechanic tested catalytic converter and said that is not the problem. When you start out in 1st gear you can just barely push the gas pedal or it will bog down to nothing. Once into 4th gear it seems to run OK as long as it's a straightaway, if you hit a hill all power is lost. You get nothing when you give it gas. If you rev the engine in park it backfires. Any help is appreciated becuase he won't take it to the shop and I'm left trying to figure it out. He changed the plugs about 2 months ago.

Backfire is coming from the engine and not the exhaust. Check engine light is on. I could take it and have it checked free on the machine but it is running so bad I'm afraid to drive it far. I was just reading about the MAS and I think I'll check that in the morning. I don't know how to check the fuel pump pressures. I will check for vacuum leaks tomorrow though. I know I can start out replacing basics; plugs, plug wires, etc. I know so little about auto repair. Would a vacuum leak cause the symptoms I described?