computer says misfire #3, i replaced #3coil,plug and wire we're thinking val job

Check the compression, look for a vacuum leak at the intake manifold and "listen" to the fuel injector to see if it is firing. Using a mechanic's stethoscope (or use a long screw driver placing the handle end up to your ear place the metal tip end of the screwdriver against the body of the fuel injector), get a friend to crank over the engine while you "listen" to the fuel injector listen to each injector at the same point of the injector body. You should hear "click, click, click" as the injector is electrically opened and closed by the computer. If the injector is not being triggered you will not have fuel getting into the engine's cylinders. The coolant loss, were the cylinder heads pressure tested to see if they were cracked or porous.