I would advise re-calculating how many kilometres your car has run on this CVT oil that you are using, as a starter. If you are a second or third owner and havnt replaced it, do it immediately. Honda advises it to change at 40k for harsh environments. But since our traffic routines are sometimes more than harsh, its better to change it a 30k.
Coming to you problem. The symptoms you are giving, if i rephrase them, is that on AC in P or N mode, you dont feel any problem. Its only in D when you stop at a signal that you feel vibrations????
If my understanding is correct, this is not an idling or IACV issue. It has to do with your CVT start clutch. While you are standing with brakes applied in D at a signal or stop, the gearbox start clutch should disengage. This is a trait of CVT in 4th gen. It does not have a torque converter. The engine+transmission should not try put the vehicle in creep while brakes are applied. Otherwise you would feel vibrations and the CVT belt has to bear the consequences in the long run.
What you need is a start clutch calibration. It is done whenever the battery is re-installed, ECU fuses are replaced or some work on tranny is done. Most people dont know it while honda has offered service bulletins in the past for this model.
Reset the ECU. Remove battery negative for more than 10 seconds. Preferably wait for about 10 mins before re-tightening the battery negative terminal
Start your car and warm up till you can hear radiator fan turning on.
Turn off the car. And Restart again. Dont use any electrical accessory yet(AC, Power Windows, Radio nothing)
Turn on your head lights.
Put the car in D and drive off to a clear road.
Take the vehicle speed upto 60kmph. Once there, let go of the accelerator and let it cruise down for more than 5 seconds WITHOUT applying brakes. I repeat "Do not apply brakes during this time"
Do the above step one or two times.
Your start clutch should now be calibrated.
Second procedure is by shorting the SCS pin in the DLC with chassis ground (Infact shorting Pin 4 and 9). But lets try the above procedure first shall we.
Alternatively you can take it to Honda guys and they will do it for you.
The result you should be getting is that, you should not feel very low rpm at stand still. Second, if you release the brake quickly and observe, the car should start creeping after about half a second.
This would infact put more load on the tranny as engine is trying even harder to move the car with brakes applied. Its a temporary but more damaging solution in my humble opinion