Help with car problem

[Nite Owl]

My son's girlfriend was driving and her car couldn't get over about 50mph then the speedometer would say 70mph but she was going about 40. It felt like it wouldn't go into gear. It also had trouble starting, it would turn over but then stall. It's an '01 Kia Rio with about 100k. It has to last a few more months and then the loan will be paid and she can get rid of it. Any thoughts on what it could be and how expensive? My son and his friend can probably do the work.

[Blue_Tires]

1. not sure i can help

but do an online search for possible TSB's or common problems