2001 Chevy impala will start but won't accelerate

Has the trans been serviced regular and is it low on fluid. How long has it been since trans filter has been changed? Does the trans fluid look dark or smell burned? Is there any check lights on dash and if so have the codes read at a auto parts store, Trans codes need to be check by trans code reader to check them, but it could be one of the solenoids or sensors in the trans. So you will likely need to get it too a trans shop.

Fluid is full but I haven't changed the filter in a long time. It's a little dark but I was worried if I did change the fluid not owning the car for more then a couple years now I didn't want to chance hurting the trans. I own a code reader myself and the only codes on that is the o2 sensor and egr which I had already replaced but the code never went away

Need to look up all reason for that code to come up and see where it leads you to. You can change the fluid & filter just do a manual drain and not a power flush and add Lubegard additive per directions on bottle to fluid before filling it up. There is a few varieties to choose from. Just read up on which is best for your car, that has the needed friction modifiers. BUT If your trans is already slipping and needs rebuilt then no additive will save it, it needs replaced or rebuilt.