1nz low idle

[2zz corolla]

Hi there sorry if this has been discussed before. I did a bit of googling and aparently it's normal but I don't understand how Toyota could sell cars with such a rough idle.

2001 echo sportivo

120k on the clock

The car is perfect when cold but as soon as it heats up the idle can go as low as 500 usually sits at 600. It doesn't idle hunt just feels very rough. If I turn air con on the idle increases slightly maybe 100-200 rpm.

Surely this isn't normal??

Because its a older 1nz it has cable throttle so I was thinking of just adjusting idle screw to increase idle but I'm wondering if a sensor may have failed. Car is perfect otherwise.

[STLTHZR6]

Airflow meter? or O2 sensor?

[2zz corolla]

Mm I cleaned the maf but haven't had a chance to check o2 the car does smell like it runs rich. Other then that runs perfect and fuel efficency seems very good. Maybe I need to clean idle speed control valve looks like a nightmare to get to though.

Another werid thing I noticed Is after 20 min drive idle seems to correct it self.

So to recap cold idle perfect

Engine up to temp idle as low as 500 rpm

15-20 min drive idle back to 700 800

I probably should do ecu reset