I have a cold start rpm of near 2000 rpm (i heard it is not good) and
after the car gets warm without driving it, the rpm stays at around 1000 rpm (sometimes it will stay at around 1100-1200 rpm). After driving for a while, it
may or may not drop. If it drops, it drops down to 900 rpm and if I don't apply the brake, it will rise to around 1050 rpm and drop back to 800-900 rpm after
applying the brake again. If I switch on the A/C, most of time it will just go over 1000 rpm to around 1100-1200 rpm. This problem always happen at night.
The problem is a little better in morning. Because I have tried to adjust the idle screw to make the rpm as low as possible, I noticed that the idle screw
sometimes work in the morning and sometimes not. Why I say that is because in the morning, the idle rpm can sometimes be around 400-500 rpm (the idle screw played a role) and somtimes be 800-900 rpm (the idle screw didn't play a role). It happened during the same ride. I heard with no load the rpm should be 750 plus or minus 50 and with all the load on (A/C, headlight, defrost) it would be around 900 rpm.

This is basically pretty much about the problem.
As a wrap up, my car has problem with
(1) 2000 rpm at cold start
(2) idle rpm varies with/without applying brake
(3) different idle rpm when warm in morning and at
night.
(4) Overall idle rpm is too high and not consistent.

I have had my car cleaned the IACV and readjust the
idle in a repair shop and it doesn't fix the problem
mentioned above. My check engine light is not one and
my guess is some of the sensors are getting bad which
send faulty signal to ECU? or my idle rpm setting is
off(I don't think that is the case)...

Please give me a hand about identifying the problem, Thank you!

 

Correct 750 +/- 50 is the spec. It sounds like you know some **** so here goes, if anything or any words are too technical just ask for explanation. First I would make sure there is proper deflection in the throttle cable. If I remember correctly off the top of my head proper deflection is 2mm-3mm. Once that is set pull the intake off the throttle body. Is there two ports on the inside of the throttle body along the bottom? (There will be a total of 4 ports) Start the car. Put your finder over the port on the bottom that is closest to the firewall. Is there suction? If not replace the fast idle thermo valve. If there is suction warm the engine coolant up to normal operating temp (fan comes on). Check for suction again in the same port. Is there suction? YES? If there is replace the FITV. There are many many systems that can effect idle. This is where I think you should start. Good luck, and let me know how it goes...

 

where do you live??? many different factors affect idle... humidity, altitude, did you travel recently??? idle on the d16z6 is not consistant for a reason... do you have a system (cd player, subs, etc?) if so those will affect as well. many times on a honda something in the electrical system is to blame. the idle of 2000 on a cold start is normal though... that is how the car warms itself up. it maintains your reliable honda.

 

I forgot to mention that my civic is a 5 speed and I live in Southern California. I will try your advices. Thank you