On my 2000 civic cx in my opinion isn't idleing right. I will start the car up, it doesn't matter if it's warm or cold. I will step on the gas a little and rev it up, then I let the rpms fall. It sounds like it falls down to about 1200 and stays there for a few seconds, then it slowly drops to about 800 or so. I don't know exactly what rpms because I don't have a tach.
I've never worked on a civic before but it seems to me that it is a vaccuum leak, but when you let it sit there for a few seconds it idles perfect.
My other thought was that the Intake Manifold volume is very large and it takes the motor a couple seconds to suck the air to normal. This could be purposely built by honda for those people that don't have good throttle/clutch technique, it's much harder to stall a car at a stoplight when it's revving a little higher than idle.
My last though was a possible sticky throttle body or TB cable.
Let me know what you guys think. I am new to the forum and hondas so I thought I'd post this up.