But still my engine is making back-fire noises and running rough due to misfire?

Alright, Yesterday I bought and replaced a new distributor. My old one went bad after 18 years go figure. Alright I put the distributor in bought a timing light and timed the distributor perfectly! But still my engine is making back-fire noises and running rough due to misfire. Does anyone know what I can do to fix this problem? I have already bought a new distributor cap, wires, and plugs about 2 weeks ago before the distributor went bad. Please help me out! This is my only way of transportation and its already been gone for about 1 week.