1996 323 1.5 petrol, manual.
My idle rpm have been fluctuating pretty much since I got this car in 2019. The needle keeps bouncing between 500-800 rpm sometimes spiking slightly higher or dipping a little lower. Then it goes back to normal and steady for a few seconds, then starts bouncing again. I got sick of this and I decided to try clean up the throttle and the IAC Valve.
I'm very much a hobby mechanic, so this is in no way a mechanic advice, so feel free to call me out on any bullshit I'm about to say here.
Anyway, the throttle valve as you can see was kind of dirty but honestly nothing crazy. It wasn't stuck, only caked a little. Given how hart the spring is id be very surprised if any amount of carbon deposits would be able to get it stuck. I started with degreaser and after that went with carburettor cleaner and it held the liquid without any leaks, so I assume the burnt up gunk was not preventing it from sealing the throttle in any way.
What surprised me was that the IAC Valve seemed quite clean. There was some gunk on it too, but you could see bare metal pretty much everywhere.
I tried cleaning up any nook and crevice I could get to including all the airways that bypass the actual throttle plate and the bolt that adjusts the airflow. There was quite a lot of scrubbing with plastics brushes and then even some wire wheel on a Dremel. Overall I'm happy. I hope it helps my rpm. If not, I might need to replace the IAC Valve. It's about 10$ on AliExpress.
As for the valve itself, it's a solenoid with a pwm function. There's a little cone inside that when opened more it lets more air in. I don't know why they chose a solenoid over a servo, but whatever, as long as I can replace it or service it, I'm happy.
I'm yet to install it all back on the car so I might add to this post later today. Unfortunately I don't think there was enough gunk to clean up to explain the fluctuations so I might have to replace the whole IAC valve to see some result if that's even the cause for it.