knock sensor location

91 acclaim, runs way rich only getting 12 mpg strugles to run sometimes but not all, only could go 50 the other day then all of a sudden ran great, just changed o2 sensor fuel pressure regulator cap rotor wires plugs air and fuel filter, dont know what else to do, oh ya looked at cat and was not plugged. This knock sensor may be my only hope.... if i can find it. or does anyone else have any ideas THANKS