I already had the coupler fixed on my washer and now it is doing a slow agitation to wash my clothes. My clothes are not really being washed as good as they did. The water is draining and everything else is working fine, just slow agitation. What could be the problem and could I fix it by buying a part?

There are 4,378 different washers made over the years and the problems with most of them are different. Needless to say I am not going to list every problem that every washer could have since my time is limited. For better answers to your questions you need to include the model number and brand.

One quick answer for you. The possibility of fixing you washer by buying a part is almost nill unless you have the tools and the knowledge to do the job. Most agitation problems are caused by the drive system which can be complex in nature.You said you had the coupler fixed on the machine. I would call the repair person back and see if they possibly caused or missed the problem when they were there if they were there just a short time ago and the problems could be associated together..