Fuel injected engines can't use an idle screw, they have no jets to add more fuel when adding more air, so engine would run too lean when idle is increased using a screw on the throttle plate.
So they all use an IAC(idle air control) Valve controlled by the computer......which also controls the fuel.
When a fuel injected engine is started cold(without touching gas pedal) the RPMs should go up to above 1,500, then drop down to about 1,100-1,200.
Thats the computer opening the IAC Valve all the way, then closing it a bit to set cold idle, cold idle is based on engine temp, colder engine higher idle, this is "choke mode", a computer routine that runs high idle, advanced spark timing and richer fuel mix.
If the above is not happening then you have a problem, most likely IAC valve needs to be cleaned or replaced.
Warm engine idle should be 650-750rpms for manual trans vehicle.
On '95 and newer engines/computers(OBDII) with manual transmission there is a fuel saving method that causes computer to hold idle at or just above 1,000 RPMs when speedometer is above 5mph and clutch pedal is in.
When clutch pedal is in and you are 0-4mph then idle should be 700 warm or 1,100 cold
O2 sensors are not used at idle, and stalling would not be a symptom of O2 issues.
Fuel injector issues cause misfires or loss of power at higher RPMs(not enough fuel)
And these would also cause CEL(check engine light) to come on
TPS(throttle position sensor) on the 2.3l/2.5l engines can cause odd ball stalling.
They can be tested with volt meter.