I have a po304 & a po171 code what do you think is wrong

all misfires and bad mixture of fuel and air

https://www.google.com/search?q=05+TAURUS+CODE+SHOWING+po171+po174+po300+pO303+pO304

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That would require a detailed procedure so its carried out properly
u can get a manual for help..
I keep getting those for vehicles too.. I know a lot of websites and which one is best for what type of vehicle.
and some are just useless, no customer relationship management..

Do tune up,coils module,wires,plugs and see what happened..

THROTTLE POSITION SENSOR, MISFIRE, #4 MISFIRE, KNOCK SENSOR, THESE ARE YOUR TROUBLE CODES, PO120,PO300, PO304, PO325, RESPECTIVELY, REPLACE THE TPS @ THROTTLE BODY, REPLACE KNOCK SENSOR , @ ENGINE BLOCK, REPLACE YOUR SPARK PLUGS & PLUG WIRES ! AND YOU MUST ALSO REPLACE BOTH YOUR AIR & FUEL FILTERS, DISTRIBUTOR CAP & ROTOR , INSPECT, MAY NEED TO REPLACE, I WOULD ANYWAY !!!!!!!! ADD SOME GOOD FUEL INJECTOR CLEANER TO TANK, NEXT FUEL UP !

Cylinder misfire on # 4

Google----OBD2 Codes 2004 ford PO304
& learn about that

You should be replacing all upstream oxygen sensors,
the ones at the inlet or pipe before the converter,on all
your vehicles at 100,000 miles

Go to Rock Auto.Com & buy two & install yourself

NTK 22060 $26.79 ea

PO 301 thru PO 308 are engine cylinders with possible
misfires & bad coils

PO 171 is a lean condition on Bank# 1 oxygen sensor

If the front or upstream sensor are over 100,000 miles, change
them as preventative maintenance

The cylinder misfires have to be diagnosed & tested any of
several ways,professionally for the most part

We can't help you here

You need the car diagnosed

I doubt you have lifters,should have
OHC valve train

Most likely the oil passages are clogged up
in the cams with sludge

That's what happens when the wrong oil
& too long between changes takes place

You ruin the engine

PO121 : TP Sensor Performance = The PCM supplies 5V to the TP sensor(throttle position). The TP sensor is a variable resistor that drops the voltage to about 4 volts at WOT(wide open throttle) to less than 1 volt at closed throttle. Some TP sensors are adjustable. others have a learn procedure to determine closed throttle. PO171 Fuel Trim System Lean = In closed loop the PCM adjusts fuel delivery based on H2OS 1 readings and is indicated by long & short fuel trim values. If lean the PCM will add fuel (fuel trim above 0%) & if rich the PCM will reduce fuel(fuel trim below 0%) PO128 ECT Below Thermostat Regulating Temperature = possible failed thermostat, low or empty on coolant, Engine Coolant Temp Sensor, Poor connection/Harness/Wires, faulty PCM Connection. I think you hit the nail on the head , the ECT Sensor ( which is different than the temp sensor for the dash gauge)

complete tune up plugs wires distributoe cap and rotor