Low idle only in warmer weather

[98civex]

So today outside temp was near 60 around here and a problem I had forgot about resurfaced as it usually does in warmer seasons.

After my 98 civic ex manual transmission reaches op temp the idle gets extremely low and sits at the notch right above the 0 (500 rpms?). With lights on the idle is fine and more in the middle of 1 and 0.

Otherwise when the temperature outside is colder (below 45 degrees) it usually idles more towards the 1 on the tach. Is this low idle normal for warm outside temps?

Things I've done/tried in the past:
Idle relearn procedure
Changed pcv valve
Complete tune up
Cleaned throttle body and iacv

Only thing I've yet to do ever is replace fuel filter. I've read that it never needs to be replaced in our cars. True false? Would it contribute to this issue?

 

[HeX]

It is perfectly normal for the engine to rev higher at a cold start-up during low temperatures outside. The engine intentionally does this to warm up faster. This is why in warmer temperatures it wont rev so high on a cold start-up. It simply doesnt need the extra reving when its warmer to reach normal operating temperature.

 

[98civex]

It is perfectly normal for the engine to rev higher at a cold start-up during low temperatures outside. The engine intentionally does this to warm up faster. This is why in warmer temperatures it wont rev so high on a cold start-up. It simply doesnt need the extra reving when its warmer to reach normal operating temperature.

I get that, but that's not what I'm asking. When it's warm outside and my car is at operating temp the idle is super low, sometimes almost stalling. But when the temperature outside is colder like in winter the idle is fine/where it should be

 

[HeX]

I get that, but that's not what I'm asking. When it's warm outside and my car is at operating temp the idle is super low, sometimes almost stalling. But when the temperature outside is colder like in winter the idle is fine/where it should be

Then it sounds like you should adjust the throttle up to about 700-800 rpms while the engine is warm. 500rpms does sound a bit low but then again your description wasnt exactly clearly written.

 

[Charlie5280]

this is normal