Ranger jumping when acce;erate

I have a 1993 Ford Ranger 2 wheel drive with a stick shift. It has the four cylinder engine it it. I have 191 000 miles on her. Until recently I have only had to perform routine maintancence. It has been a great truck.
the truck starts great and idles fine, but when I mash on the gas peddle it bucks, lurches, stutters, and hickups. It gets better after the truck warms up. I have also noticed that it does it less when the vhicle has a good amount of gas in it.
It seems as if it is misfiring or maybe not getting enough fuel.
Any help you can give would be great.