shifting problems and gas pedal.

I have an 89 Buick Century with a 3.3L engine. When I start the car and drive, the gas pedal is hard to push down. After driving for a while I will press the gas hard for a second then it becomes loss but, the car has high rpms before shifting. It will shift at about 4,000 rpms with the gas pressed a little. After a while of that, it goes bat to normal. This hasn't happened till it got really cold here. Could you tell me whats going on. I just changed the trans fluid and filter.

I really need help guys.

Can nobody help me with this problem.

Clean the throttle body for the stiff pedal also check linkage for binding. As for the trans, check for vacuum to the trans modulator, should be on the lower ft l/s of the trans case.