Number four cylender is dead as four o clock. checked fire on plugs and wires. they are fine. pulled number four injector, no gas spraying. can i take the injector apart

Code 306 means cylinder 6 is not producing power. And as you know it takes fuel, spark, and compression at the right time to make power.
Generally, if the injector is firing at the right time the spark plug should be firing as well.
Are you sure the plug is firing ? And is it possible injector 6 has no fuel to spray ?

What test told you it is not firing?

You may have valve damage &
little compression

use a digital volt meter,put it on the ohm scale check number 2 fuel injector should be 11 to 16 ohms if not reads zero fuel injector faulty.if numbe 2 fuel injector okay.use noid light hook it to fuel injector electrical connector with fuel injector disconnected and see if pcm is firing the fuel injector noid light should blink when cranking the engine.if light steady pcm not firing 2 fuel injector,if noid light dont light up.there is a open in the wiring connector 2 fuel injector 2. if fuel injector okay,check spark plug, carbon foul you have a bad ignition coil or wire if you see oil on spark plug you have worn piston ring or leaking valve guides allowing oil to foul out spark plug.do a compression test check compression to see condition of the cylinder.

if the rough idle stays on those cylenders check plugs for wetness check coil plugs fore bad connections or broken wires check injectors and injector plugs

check fuel filters, and try running a fuel injector cleaner

Some Ford engines are not equipped with knock sensors. Yours may be one of them. Located in the wiring loom, close to the ECM, is a "jumper" that when removed retards the timing 4 degrees. This should correct your pinging problem. as for the missfire try changing the plugs and wires .also check the egr valve. thanks

Its easy enough to check for spark but how are you checking that you are really getting gas. Are the spark plugs new. If so the check that you have the right ones. It is not uncommon for a parts guy to give you the wrong plugs . If the plugs are not new and the car was running fine with those plugs before all this happened and the plugs look fine now, no bad, black carbon deposits then lets move on . Did you just put gas in the car. sometimes you can get a load of bad gas, I mean water in the gas when I say bad. Been lots of rain lately and this does happen. Pull the plugs on the car and spray some starter fluid down the cylenders. Replace the plugs and turn the engine over. If it fire up for a second or two and then quits, I would start looking at the fuel system. The fuel solinoid relay, which would supply power to the fuel pump could be a problem. Be sure you are getting fuel in the cylenders.

do a compression test on all four cylinder to see if it has low compression. you may have a blown head gasket or burnt valve.

One solution to no fire to the injectors is to turn the key on and put a 12 v test light on the injector plug to see if it has fire . if it does not, a common problem is that there is a short in one of the three red wires ( green plug) coming off positive battery terminal. Test (test light) each small wire coming from + battery and if you find a dead one, it has probably broken inside the wire insulation and you can cut it and resplice to a good hot wire. Mine was the hot wire to the injectors !

NOW VERIFY IF THE INJECTORS ARE FIRING OR CLOGGED OR THE COIL PACK ISNT FIRING.GET A FUEL PRESSURE GUAGE & TEST LIGHT TO HELP YOU OUT.IF YOUR SURE ABOUT THAT TRANS FLUID IN YOUR GAS TANK DEFINATELY CHANGE THE GAS FILTER & PUT SOME FUEL INJECTOR CLEANER IN THE GAS.AFTER YOU FIGURE OUT YOUR PROBLEM.GOOD LUCK