My 03 wrangler will not rev past 3,500 rpm

o2 sencer

It only revs up when u start the first in the morning? If so, it is normal, once it warm up it will back below 1000 rpm.

check the fuel pressure and the fuel filter. You've eliminated the ignition probables.

Sounds like you have an injector leaking. Have someone just cycle the key on and off to run the fuel pump but don't crank the engine. If you see fuel dripping from the injectors, unbolt the injector cover on the throttle body, remove the injectors and replace the orings around the injectors.

Do you have the idle speed turned up to keep it from dying? Because it is high. Check engine light on? Have you checked for vacuum leaks at the gasket under the throttle body? How does the car run under acceleration? You might have a worn distributor shaft.

disconnect the throttle cable from the throttle body and try to rev the engine

if still cannot rev past 2000 then suspect MAF (mass air flow sensor) or the throttle body...remove the snorkel and check to make sure the throttle plate is moving freely

finally, if when the accelerator cable is removed and rpm's rise above 2000 then suspect the accelerator cable and/or gas pedal

Idle is factory set and cannot be adjusted, your best bet is checking for cracked hose pipework for air intake at idle,(not at problem under exceleration and driving) Any slight upset to the air /fuel ratio will be most prevelent at idle speeds.Check hoses where the meet metal flanges on manifold intakes and any sharp bends in ppipes.Good luck

bad fuel pump can cause this or plugged fuel filter but i believe they are one unit

The check gauges light is normal because at 400 rpm it isn't running fast enough to build sufficient oil pressure. I am guessing maybe a vaccum leak???

Check the computer on the car it may be programmed to run still on 2 K rpm you need to reprogram the computer on your car.......