Changed Plugs,coil Packs And Injectors And Still Misfire #4

I have changed plugs, coil pack, injectors, O2 sensors, MAF sensor, air intake sensor and still getting code p304 which is a misfire #4 cyl, But it is the only code now...... idles good and starts missing on acceleration unless i baby it! i can hammer it and sometimes it will clear out and run great with great power its like it is hit and missing under load then back to good idle, I can hear it spit and sputter out the tail pipe with rear window open when under load. any help would be great. LOST!!!! thanks.............

I have changed plugs, coil pack, injectors, O2 sensors, MAF sensor, air intake sensor and still getting code p304 which is a misfire #4 cyl, But it is the only code now...... idles good and starts missing on acceleration unless i baby it! i can hammer it and sometimes it will clear out and run great with great power its like it is hit and missing under load then back to good idle, I can hear it spit and sputter out the tail pipe with rear window open when under load. any help would be great. LOST!!!! thanks............. coil pack ground for a 5.4 expedition does anyone know about or where it is ?? i read it on here but never said location or if it has one. thanks........

Computer grounds 1997 5.4L 1.Rear of engine compartment,right side of cowl panel. 2.Lower left cowl panel. 3. Rear of engine compartment on right side of cowl panel.
Some times depending on mileage you can have a worn valve guide and the rocker arm turns and the valve doesn't work correctly. If you put your fingers on the valve spring you can feel it. It was very common on the old chevy 305 engine. Try a compression test as it will show up if it happens during the test.
Could be a weak valve spring.

ill check the compression but would it have a full time misfire if the guides were worn out because mine idles good starts missing at about 1700rpm's after that good, did have a code once that said #4 to rich but always # 4 something?hmmm. Im lost really!!!!do you think if the pass. side cat is pluged up would it misfire # 4 first? it has 150000 miles on it, The New Generation Star testers are not all that good, gives code but same as autozone if you dont have the book (OBDll) i dont know....thanks for your help

If you used double platimum plugs if I remember correctly on one side you had to pull the fuel rail to change plugs. Spray around the injector base with carb. cleaner if it smooths out install new o-rings. Coat them with vasoline so they go in smooth and don't tear. Also spray around the intake manifold and pinch off the hose to the vacuum booster.
Buy a noid light and check for blinking when cranking. Watch for a dim or weak flash. A bad electrical connection will cause an occasional miss.
Your other question as long as the valve is straight it will run fine. Once it twists the valve leaks and you have a miss.
On a plugged cat. Put the vehicle on jack stands and loosen it up on front side of the converter. Pull it back about 1 inch if your problem goes away buy a new cat. Depending on how long you had the miss this could be a problem.
A Chevy will not work on no.4 cyl if your fuel pressure regulator is going bad and will foul no. 4 but the other cylinders will run lean. Pull the vacuum hose for the pressure regulator if any fuel install a new one. Have you changed your fuel filter. It would be a good idea to check your fuel pressure.
If these ideas check out I will check my ford factory manual for you.

i did use platimum plugs not double, the fuel rail had to be pulled on the drivers side not the pass when i changed the plugs. i aso changed the fuel filter to and i put new injectors on the passenger side and used vasoline like you said. im gonna do a compression test tonight and check the vacuum and the fuel regulator, i just cant understand if its a vacuum leak or fuel problems why does the OBDll keep saying #4 misfire. i have gotton some other codes to, ill clear the codes before i go to work and check them when i get home and post them. thanks alot for your help....

The computer measures pulses from the camshaft position sensor. It checks timing from the crankshaft position sensor. It checks tempreature from the temperature sensor. It checks fuel mixture from the oxygen sensors. If the fuel pressure is wrong No.4 is on the end of the line. If the fuel pressure is low it won't fire properly. This would slow down the time until the next piston fires. A vacuum leak would change the mixture and it wouldn't fire properly.
Hopefully this will help you understand.

thanks helps alot, im use to the old school cars when you spray carb cleaner on the intake to find a vacuum leak it would speed the motor up these actualy level out not raising the idle but smoothing it out. so i retested for a vacuum leak and it smoothed out or a sec. and actually ran better after i sprayed it, only code pulled up after the drive to work and back home was p0446 which is Evap system, Vent Control Malfuntion. there is a cylenoid in a canester in the rear of the truck that measures gases. checking vacuum line tomm. to tired tonite lol any tips would be great about a vacuum test, thinking of plugging the main vacuums at the throttle body? anyway thanks for the help...........

Their was another thread about this and somebody said their is a hose on the back of the manifold that leaks and causes problems. Repairing plastic vacuum lines I've had good experience using rubber vacuum hose cutting it and sliding the two ends of plastic into the rubber hose. Buy a vacuum gage and check for vacuum at the canister if you have vacuum at the line to the cannister make a tee in the line and check if the canister is leaking. Then either a new canister or junkyard for a good used one.
According to a 1997 5.4L F-150 you have main Vac red goes to FPRC,black goes to 17cu in vresserand a 166 cu in vresser, then a white goes to EVR,green to EGR, Tan goes to VMV,which goes to a tee for the fuel tank and vac cannister It also shows a dotted line from the man Vac to the VMV.
I know ford puts 1/2 the engine under the firewall but I think you found the leak spraying around the intake. Follow the black to a tee for 4x4,4x2 axle disconnect solenoids,past the tee for vacuum control valve down towards the vressers. I think it will be close to the intake. To use a vacuum gage you need some plastic adapters that change size and a tee the same size as the gage line. You will need some various sizes of vacuum tubing.