I am trying to get to the bottom of this problem on my mom's 1997 Ford Taurus LX V6. When I try to rev the engine it stops at around 4500 rpms and hesitates it will not allow it to go any higher and it just sputters and the rpms drop, the engine does not die though it remains steady but just will not allow the rpms to go any higher. The car has had a recent tune up i.e. plugs, filters, wires, etc. etc. I know I probably described this poorly, so if you need anymore info let me know.