I have a b16a2 engine and my idle fluctuates after coming to a stop. From like 1k to 2k up down up down continuously. I've clean IACV and still does it. When I turn on AC the idle fluctuate stops. What should I turn to next? What else should I check?

 

Have you tried bleeding the coolant might have bubbles in it. That can cause fluctuation in idle speed.

 

If u have a non stock intake this can cause the idle to fluctuate because of the extra air coming into the motor at idle. I fixed this problem by making sure my throttle plate is completely closed and messing with the idle screw. For a stock ecu

 

How would I bleed coolant system? Let it run with radiator cap off? Let the bubbles come out?

 

It's non stock intake. And how do you adjust throttle plate if it isn't completely closed? I can't find an idle screw on my throttle body either. Should all have? And I have spoon ecu

 

Yes that what i do just take the radiator cap off when its cold and turn the car on and let it run till its at operating temperature and the bubbles will come out....some honda motors also have a coolant bleeder valve where the upper radiator hose connects to the motor....easiest is to just take the cap off...hopefully this helps

 

I dont believe the intake has anything to do with it, i think you meant the throttle body....if your throttle body for some reason doesnt close properly them i could see that causing a weird idle because the iacv would allow air in and at the same time the tb is allowing air in....this usually only happens with a bent throttle plate or if someone messes with stop adjustment on the outside of the throttle body where the spring mechanism is

 

Sounds right. But my idle stops fluctuating if I turn AC on, does this help?

 

dont fck with throttle plate its gapped for a reason so it doesnt stick.
adjust the screw instead and check iacv operation and fitv leaks

 

As raverx mentioned, if you have a fitv google how to rebuild fitv honda

 

Thanks guys I will try those and see how it goes

 

besides vacuum leaks from outside theres only few places that air comes into the intake manifold

1throttle body plate
2idle adjusting screw
3IACV inlet
4FITV inlet only when warming up( bottom hole in throttle body should not have any suction when fully warmed up)
5pcv valve from crankshaft
6pcv valve from brake booster
7electronic valve from evap canister purge solenoid

fitv currently is what im having problem with

 

Moving this to Tech

 

Ok first do the easy stuff. I hate idle problems and have learned that diagnosis is key.
First do the easy stuff.
Bleed the coolant
adjust your tps sensor(easy just need multimeter )
clean the fitv ( there are threads on how to do this)
CHECK THOROUGHLY FOR VACUUM LEAKS

Adjust idle screw after doing these things. If those did not work, remove your iacv and use two pieces of wire and connect them to your battery + and - terminals then touch the wire ends to the sensor on iacv where the plug goes normally.

Did the gate on the iacv click open and stay when given constant voltage? Did it flutter open and close? If it stays open under voltage it is a good iacv. You can hear it distinctly open and close.

If you rule the proper function of the iacv next replace the small rubber gasket on the iacv it could be causing a vacuum leak unseen.

After ruling out all of the above double check your throttle stop screw. It is a small little screw under your throttle where your throttle cable connects. It stops the throttle just a hair before it closes all the way so it doesnt get stuck closed. You want to screw it up till it just barely presses the throttle open. Really just barely!!!

If all of these things check out I would next assume it is a bad tune and could be fixed by changing up the fuel mixture, ign timing, and iacv duty cycle at idle.

Has your car been tuned before?