Engine Losing Power and Shaking

[Aaron_99TI]

Hey guys, I'm having trouble with my 99ti. Today out of nowhere my engine lost alot of power, and was sputtering a little. There was a shaking that went throughout the car and seemed consistent with a miss..

What surprised me was that after a few hours of leaving the car off, it drove fine for a few minutes then went back to the shaking and no power. The check engine light is on, and has been on for a while due to an O2 sensor needing to be replaced, but it flashed while i was driving at one point..

Also, yesterday we had a lot of rain and slush, so I'm thinking that may have created some dampness in the electrical system.

Any help on this would be greatly appreciated, I'm a poor student at the moment, so garage trips are a little costly, especially since it would cost over 800 bucks just to get to the closest dealer..

Thanks again..
Aaron