Have a 2001 ford expedition with a 5.4 triton has a misfire in the number 3 cylinder i changed the spark plug and the coil pack on it confused on what it could be that keeps throwing these codes

Vehicles: Any vehicle with the above symptoms.

You have a bad spark plug wire on #3, or possibly a clogged/malfunctioning fuel injector on Cylinder #3. Or, less likely, some of the other possible culprits mentioned below (exhaust valve/O2 sensor/Catalytic converter/ECC).

I'm presuming the OBD-II DTC code from the Expedition's computer is P0303.
Always try resetting the code and see if it returns - your new spark plug and new coil pack may have fixed the problem, but if the P0303 code isn't reset, it'll remain stored,and the CEL (Check Engine Light) will remain lit.

If I were standing in front of the vehicle right now, the 1st thing I'd do is put my "mechanic's stethoscope" on the fuel injector with the motor running to verify correct operation. Why would I do this first? Its free, and informative. You'll hear both the explosion in the cylinder, and the "tic" sound of the fuel injector solenoid as the injector operates. Auscultate the properly functioning cylinders first, so you know what to listen for.

If all you have is a medical/Sprague-Rappaport stethoscope. remove the auscultation bell, and replace it with a 12-inch (36 cm) long wooden dowel or solid/hollow metal rod as a substitute. Sound will transmit just fine through the wood/metal. Prefer metal, if you have a choice.

Here's the "official" P0303 write-up:
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P0303 Code - Cylinder #3 Misfire
Technical Description

Cylinder #3 Misfire Detected

A P0303 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #3.
Symptoms
Symptoms may include:

the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present

Causes

A code P0303 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer (ECC)

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. In other cases the problems were faulty fuel injectors.