same thing happened to my civic.

* Clean the Throttle Body. http://www.ozhonda.com/forum/showthr...highlight=IACV
* Clean the IACV filter. http://www.ozhonda.com/forum/showthr...highlight=IACV


If the engine is a D Series:
* As above, and Screw in the FITV valve. http://www.emotors.ca/Articles/97.aspx