Problem just started. Idle very rough, doesn't stall out, but close. If I put in neutral, it will raise idle slightly. If I give it a little gas, say 1100 rpm, it smooths out. I thought maybe it was the O2 sensor and replaced it, but still same problem. Once the car is running at a higher speed, it is fine, though.

Any suggestions before I take it to a mechanic? Thanks for any advice.

 

any codes? check engine light on?
kinda sounds like a fast idle valve...
you might wanna check it.. got this out of a honda accord manual...
1. Start the engine.
2. Remove the cover of the fast idle valve.
3. Put your finger on the valve seat area and make sure
that there is air flow with the engine cold (coolant
temperature below 30°C, 86°F) and idling.
If not, replace the fast idle valve and retest.

 

You can also remove the FITV and clean it out. There's a float of sorts inside that can loosen up to the point where it causes issues like this. It's what makes the engine run at higher rpms when cold.

 

Mine did same thing I just increased the idle speed.