The idle revs on my HCH2 are very unsteady on a cold start - this morning it randomly alternated between 500rpms and 1000rpms every second while I was at a red light. I just been driving the car for around 5 minutes after not driving it for 3 days or so. Last week I didn't see this issue, so it seems to happen when the car hasn't been used for a while, though sometimes the idle revs are a little unsteady, but never to the extreme I saw this morning. The idle seemed ok again after driving for about 30 minutes (though still some slight wavering as I always see it do). I don't think this is related to the small crack in the transmission mount, and the transmission fluid has been replaced so I don't think the transmission is the issue here.

Also when accelerating from idle, sometimes the acceleration "pulses" up to around 15kph, like the unsteady idle wavering somehow carries over into the regular acceleration for a bit. When auto-stop decides it's 1 billion conditions are met and works, I don't get the idle issue (obviously) or the pulsing acceleration.

I think this might be the idle air control valve, but not sure exactly. To maybe diagnose this, I want to try cleaning the valve, to see if it improves. Can anyone point to directions on how to do this for the Honda Civic Hybrid specifically?

Also any suggestions on what else it could be?

 

Here is a video of the problem in action. Some notes on what seems to cause it:
* Accelerating makes it stop, it does it on idle. Sometimes jerky on acceleration when it does this.
* Worse in stop-go traffic.
* Worse when coming to a stop on a hill, up or down.
* May be worse when the 12v battery is a bit low?
* Didn't do it much when I had some Chevron Techron fuel system cleaner in the tank. Now it is "plain" gasoline again, it is a lot worse and more frequent.

Video here: https://i.imgur.com/cKoAlXW.mp4 - note I'm just holding my foot on the brake and not touching the gas pedal.

23rd November 2018 Update- Solved!
The problem appears to have now disappeared. Using 3 bottles of Chevron Techron (adding one when the car was at a quarter tank for a more concentrated treatment), as well as Seafoam Spray through the air intake, the problem is resolved and idle is nice and steady all the time now. Either this was a clog in the fuel system somewhere that the techron broke down, or carbon build up on the throttle body or elsewhere that the seafoam spray cleaned out. I have details of these products on my site: http://hondacivichybrid2.mooo.com/#engineperformance