'99 Contour in serious trouble, dont know what else to check

I own a 1999 Ford Contour, and it is breaking down. When I try to dive it, any time i press the accelerator, it bucks wildly and tries to down shift. I realize this could mean one of thousands of things, but let me tell you what I have already done. I checked the Throttle Position Sensor, and replaced it, I replaced the fuel filter, there was about a half inch of oil in two of the four spark plug holes, so i removed them, regaped them, and cleaned them, but that caused the engine to start smoking. I have ruled out trouble with the transmission because the engine does this when i gas it in park/neutral. I also checked the fuel pump, and it sounds like its staying on for as long as it should and turning off when it should. I recently put about a gallon of gas into it from one of the cans we keep in the barn (i thought it was empty, but it had a full tank of gas) So i was thinking it might have been some old or bad gas. If someone could please point me in the right direction, it would be greatly appriciated. I am unable to take it to the shop because i live 30 miles out of town, and I really dont want to risk driving it that far

Sounds like your valve cover spark plug gaskets are bad. I cant imagine a car would run very well since oil covered all over spark plugs.

Im not a expert and i have not had that problem with the contour but i had that similar problem with my corvette, if the fuel is good maybe the fuel injectors are clogged?