I tried to diagnose a rough idle on my 2005 Civic Dx with a scan tool. I came up with several possibilities. I started with a tuneup and replaced the ignition coils. I replaced all four injectors. I replaced the head gasket, water pump and timing belt. I cleaned out the throttle body and intake. I also replaced the air intake sensor. I also confirmed fuel pressure at 49 psi before the regulator. The engine is running better, however it continues to have idling issues. I could use some expert advice???

 

I would try a new PCV valve, make sure a good seal on both ends of hose. I did that (worn part and hose was not connected properly) with my 05 civic and it did smooth out more. I am going to do the throttle body next. Just being fussy