So i have a 2000 civic ex auto sedan and it only does it at random not every single time but just randomly sometimes but when it does do it, it will do it everytime i test it until the car is shut off for some time. But back to the issue and this story will be for after the car is warmed up, but i put my car in park to grab my mail and it was idling at around 1k rpms but when i shifted into gear it dropped to around 100rpms and stalled, so after that i started it again and put it into gear and this time it went down to 100 rpms and slowly worked its way back up to 500rpms and stayed there. Is there anything that could cause this, and it sometimes randomly drops rpms at a red lights and such. Im a bit lost because ive replaced my spark plugs, wires, ignition coil and distributor cap, and i recently replaced my IACV too, and now i have no idea what the next thing that could cause it could be. I have a video of it doing it too if thats needed for further diagnosis