2. intake are control valve (IACV): most common issue associated with RPM drop when stopping, also when your aircon compressor kicks in. This version of honda city do not use an electronic sensor, the IACV is more of an actuator that controls the air flow to maintain stable idling. It controls air when you press on the brakes, turn your steering wheel, aircon kicks in, putting in D, etc. pretty much everything. this module rarely spoils but it can get dirty causing unstable idling when you do one of the above. if left unchecked, it can also lead to flywheel problem which is your next problem.
symptoms: RPM drops rapidly when you brake, compressor kicks in, turn your wheel, put on D.
Solution: just need to clean it but that's the tricky part. the IACV is screwed onto the throttle body with 4 security torx screws and no workshop have the key to open it. Honda CC will not bother to clean it for you and most probably ask you to change the entire throttle body. After some pain aching time, i got my friend to buy the security torx screw set for his workshop and i fixed the problem there.