this is a very similar problem in my civic 2005 manual. based on my observation, naging obvious lang tong idle dropping yo about 500rpm pero ndi naman namamatay yung engine pero naagapan ko by revving up a bit. typical to kapag mainit talaga panahon at stop and go ang traffic. mas madalas mangyari to kung stop and go pero during long drive ndi naman. pero kung nakatigil ang sasakyan meaning full stop or just in parking when i jerk the gas up and release suddenly ndi naman bumabagsak ang idle. naka ilang pasok na to sa honda magallanes pero ndi nila naresolve instead tinaas lang yung threshold ng idle up during aircon on and rev down para ndi totally bumagsak ang idle. i believe nararanasan ko na to as early as 2010 pero ndi ko napapansin kasi ndi pa ganun ka obvious ang prublema. naging obvious lang ang prublema netong 2016. i wonder kung naresolve na tong prublema sa thread na to para me guidleline naman ko how to proceed. i am suspecting an O2 sensor issue or electrical problem in my case.