1991 Dodge Spirit Needs HELP!!!!!PLZ

[SweetDodgeEm]

I have a 1991, 2.5 ltr., 4 cyl., Dodge Spirit. It was running great until a few days ago when the weather changed from mild and wet, to freezing and somewhat dry ( I am not sure if this actually had anything to do with the problems at hand). In the mornings, recently, I found that the Spirit didn't want to start without me putting the gas pedel to the floor while turning it over (very unusual unless I had accidentally flooded it)...then it would start and I wouldn't have too many other problems with it throughout the day. However, the last two days the Spirit has began to idle very rough...it feels as though the motor is going to fall to the ground at anytime, yet the motor mounts seem to be fine. I noticed today that the car is sounding like a motorcycle with no power...it is missing on two cylinders (the two farthest to the right). Thinking that it may be the spark plugs, I changed all four, as well as all of the wires and distributor cap and rotor (didn't think it would hurt since it has been quite awhile). These changes did not help one iota. I am now at a loss. What should I look for next? Could it possibly be the timing belt or a burned out valve or an ill fated piston or would it be something else...something quite a bit more simpler as well as cheaper(That would be the ideal situation!!)? I would appreciate all suggestions and sollutions to help me with this. Ahead of time I want to Thank You very much for your time, consideration and help. It is greatly appreciated!! : )

[theFREAKnasty82]

first, do a compression test, make sure your cylinder compression is even. Next, try replacing your oxygen sensor, it's recommended at every 50,000 miles, you change your oxygen sensor. Once you get done with those two, do a fuel pressure check, make sure it's holding between 39-50 PSI.