Po300 code misfire on my 2003 lancer how do I fix that

These numbers are OBD codes. They are misfire coding.
There is a youtube video to assist with troubleshooting.
Trouble shooting misfire Code P0300 P0301 P0302 P0303 P0304 P0305 P0306...

Good luck.
Semper Fi,
Z

PO300 and P1399 are random cylinder misfire detected.
PO301 cylinder 1 misfire
PO302 cylinder 2 misfire
PO304 cylinder 4 misfire
PO306 cylinder 6 misfire
I would say that you have damage to the ignition wiring harness or you ECM is failing.

this represents a misfire either multiple or random misfire. it could be plugs, fuel injector, plug wire,

Diagnose the cylinder misfires

Google your codes & study obd 2 vehicle systems

TYPE: PO300

Possible causes
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure
What does this mean? Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see "Possible Causes"

do some checking on the lines it will be working be sure to use from fuel.

That's a multiple / random misfire. Lot's of ways to go on this.. bad plug, wire, coil pack, etc. Then there's this one:
fixed my PO300 code MY350Z COM Forums

your engine is misfiring according to your codes ...4 codes 4 problems
P0300 - Random Cylinder Misfire DetectedP0301 - Cylinder 1 Misfire DetectedP0302 - P0312 Cylinder X Misfire DetectedP0325 - Knock Sensor 1 Circuit (Bank 1)Just showing a few

there is a code table here: code table
hope it can help u and good luck

The code P0300 is a random misfire code which means any cylinder and the code P0316 means that there is a misfire code set within the first 1000 revolutions of the engine. Good luck with this problem.