Idle rpm fluctuates between 1000 and 3000 - 2000 Honda Civic

Check for vacume leak including intake. Spray some carb cleaner around intake and vacume hoses and listen for engine rpm to change.

Resolved Idle RPMs fluctuate and engine hesitation

your idle air control valve is going out located behind the throttle body.

No such thing as a tune-up

All you did was replace spark plugs which should be
done every 3 years

Oxygen Sensors get replaced at 100,000 miles which you
also did

You most likely have an intake gasket leak,smoke test
the entire Evap System & Engine

You also are have bad igniton coils

You should remove inspect and clean the idle control valve on the throttle body. This can become clogged over time, or the motor itself can become worn and may need replacing.

You probably have a bad throttle position sensor.

The oil pressure guage will fluctuate with engine RPM. At idle it should be approximately 20 lbs./sq.in, at high revs about 50-60 lbs./sq.in. Hope this helps any concerns you may have. Good luck!

I am not familiar with this engine. But, if the alternator, PAS and AC are being driven by the same belt, then its possible that the belt is too slack, have you checked the belt tension ? That would be my first step. Hope that helps

sounds like the iac motor or the idle air control

Check that you have installed correct type of spark plugs and wires are well fitted. SPARK PLUG 3.5 V6 Type Champion RC10PYP4 Plug gap 1.0-1.1 mm (0.039-0.043 in.)