Friend has a 03 Nissan Frontier. It is idling very rough. Thinking plugs and wires. Any other ideas? Thanks

code p 0300 is random miosfires
indicates problem injectors from dirty fuel
Try a can of quality injector cleaner first in a tank to see it it smooths out
other causes include
ignition coil/s
HT leads
Plugs
Wiring but as it runs good at rpm and you have covered the rest , it is most probably sticking injector tips so use the cleaner or have the injectors serviced

this could be a lot of different things.going on here could be bad gas, clogged fuel injectors, fuel filter, fuel trim, bad pkugs and wires please tell more and what have you replaced

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 !

Rough idle?Too soon,Nissan has camphase actuator,these actuator has a tendency to get plug up and creates a rough idle,You can service these actuator both intake and exhaust,with carburator cleaner or brake cleaner even gasoline,the goal is to uplug the port

if it runs rough only at idle with the AC on then it osunds like a the idle solenoid that causes the vehicle to idle up when the ac is on. if its during the entire RPM range then you might want to check your alternator or battery, perhaps one of them isn't supplying enough power to run the engine, lights and A/C

check wiring and connection if good replace knock sensor

Don't think it's major could be any number of sensors. Any autozone will run a free scan and point you in the right direction.

This can be your Idle control valve, when you turn the air on it puts the engine under load and your computer will increase the idle automatically to prevent the engine from cutting out.
When you are standing still and the car is shaking, by touching the accelerator very softly does the shaking stop? If so check the idle control valve.
I hope this will help.
Regards
Sam

simply replace distributor cap and rotor button, wires and plugs. that will fix it

a rough idle/high idle is indicative of a malfunctioning TPS(throttle position sensor) this is located on the throttle body ,is attached with (2) screws/bolts to the throttle body housing right off the butterfly shaft. it has either 2 wire or 4 wire plug. the replacement part can be purchased at locale auto parts store. I would also agree that a full service and tuneup be done. this will help with performance and will increase the fuel efficiency. please rate this...thanks