Rice4me

Hey another question for you guys. My civic 97 lx auto sometimes tends to idle rather low when coasting to a stop, like at 30 mph for instance coasting down. As a result it would cause a bumpy downshift. I watched my tach. At 30mph the idle should be at 1 1/2 rpms or so. I have watched the tach go to an idle as if I were stopped at 800 rpms while I was still at 20-25 mph and foot of the gas, slowing down of course. Is all of this possibly from the IAC system. I have no CEL codes whatsoever and I wanted to try and pinpoint the problem. Any good info PLEASE?!! thanks in advance.