a misfire on 3 cylinder on 1997 Chevrolet Astro

changed spark plugs and wires still misfire

Asked by for the 1997 Chevrolet Astro
check for spark at # 3 plug, and take a compression on # 3 and one of the other cylinder and compared it. shouldnt be less then 20% different. finally check for fuel on #3 is that a single injector? might have a bad injector on #3 cylinder.