idles at extremely low rpms

ok i have a 1994 eclipse gs non-turbo obviously 16 valve DOHC engine anyway my engines idles extremely rough but the thing is it does it on and off though like lets say im going 35 or 40 around the city i go to slow down and my car shakes horribly and its not me stalling it out b/c i have the clutch pushed in when i slow down and it idles at like 400 like almost cutting off anybody got any ideas of what it might be????? opinions are welcome!

1994 eclipse gs nonturbo
16 valve DOHC 2.0L engine
5- speed manual tranny
140hp

so...are you saying that it will go down to 400rpm or it will act as if it was down to 400rpm?

I had this issue where it would feel like it was stalling but it wasnt, it was one of the wires on my ignition coil that had came loose. I am not sure if this is what you are asking but that is my experience.