I have a 99 blazer with a misfire on cylinder 5 I changed the fuel injector and it is still showing a missfire?

My vehicle is running rough and uses a lot of gas. Even though I replaced the fuel injector it is still showing a miss fire on cylinder 5. Any other suggestions?|||test compression. ignition, vacuum leaks on intake.|||Why would you replace the injector first? The first thing to do is replace spark plugs, cap, rotor and ignition wires - all of which are probably OE and overdue for replacement anyway. If that doesn%26#039;t fix it then CHECK for injector pulse before replacing the injector.|||You stated its missed firing, it is nothing to do with your fuel injector. You need to replace spark plugs and spark plug wires (I used the letter %26quot;s%26quot; cause it is better to change out the entire spark plugs and wires at the same time.|||Yes, Have it diagnosed by a professional. By the time you are done throwing parts and money at it you will have spent more money guessing than it would have cost to have it professionally diagnosed and repaired.|||Are the plugs and plug wires old? Is the compression within 10 lbs of the other cylinders? As a more exotic guess, a cracked or shorted coil pack on #5?|||how do you know its misfiring on #5 cylinder|||maybe it,s not fuel. maybe you have a bad plug wire or plug.