Engine misfire?

Can anyone help..can a bad fuel injector be causing an engine to misfire? Went back to mechanic, they read why the check engine light was on, and it turns out the engine is misfiring in cylinder 4, which means, he pulled out the spark plug and it seemed fine, but what could be causing the engine to misfire?

no fuel to that cylander, bad plug wire, bad plug, improper gapping on the plug, bad coil pac, bad ignition control module, bad ground, sticky injector... shall i continue??

well i got the engine misfire to stop, i took a good luck at the wires and noticed some moron put electrical tape on all 4 of the wires going into the plugs, and that they put the wrong plugs in the engine, so i got those changed, and it just so happened fixed it, the check engine light shut off on it's own..but the mechanic that did it for me said that my cooling system is all messed up, but my car hasn't even been close to over heating, and i know the guage works because i have seen it go up to almost over heating before and then it went down, i got a new radiator put in it, and they said my engine fan won't shut off, but it will shut off when the air compressor shuts off, man i wish someone could tell me what's going on..I think i need new fuel injectors..my car has trouble starting and it idles rough, i think that may be because of the fuel injectors?

well i got the engine misfire to stop, i took a good luck at the wires and noticed some moron put electrical tape on all 4 of the wires going into the plugs, and that they put the wrong plugs in the engine, so i got those changed, and it just so happened fixed it, the check engine light shut off on it's own..but the mechanic that did it for me said that my cooling system is all messed up, but my car hasn't even been close to over heating, and i know the guage works because i have seen it go up to almost over heating before and then it went down, i got a new radiator put in it, and they said my engine fan won't shut off, but it will shut off when the air compressor shuts off, man i wish someone could tell me what's going on..I think i need new fuel injectors..my car has trouble starting and it idles rough, i think that may be because of the fuel injectors?

it may be that a seal or a gasket is blown and is allowing coolant and water to seep and leak into your engine....which in turn causes plug corosion and corosion of other parts. check the plugs for corosion to see if thats why there is a rough start. it may also cause the rough idle as one of your plugs may have coroded into not working and make your car run on 3 cylinders.