1991 Nissan Pathfinder 1991 Pathfinder is Jerking on accele

It is jerking violently while I accelerate, if I take my foot off the gas pedal (like going down hill) it stops jerking, also if I put in the clutch it stops jerking. The faster I go the less it jerks. There is a sound like sounds maybe like a frayed belt flapping around and a slight smell of rubber. I know nothing about cars. But I love my Pathfinder.