erratic idle jumps up and down in neutral

Hey all. I have a 1989 Honda Civic DX two door hatch 4 speed manual with the D15 under the hood. Almost 200K on the baby. Heres the problem. when the car gets to operating temp the Idle either gets real low or revs to 3-4 or even five thousand RPMs. Its usually starts idling higher like 1,500 RPM then gets progressively higher until I either have to shut off car or a take off and start driving. I use to be able to "rev it up" once and then the idle would come back to about 900 rpm (which is where it likes to be) Now it will either idles between 300 rpm 900 and then back to 300 rpm. It does this over and over until it stalls out or I give it gas and drive away. When I get to a stop light it will rev up to 3-4-5K RPM and will need to get turned off or? So whats the problem. I have heard Hondas in traffic idle up and down real fast and wonder if this a similar issue. This erratic up and down idle is not as fast as some I've heard in traffic but maybe its the same issue just at a different stage in the breakdown process. Any Ideas on where to start with. I'm not flashing any codes on the ECU (OBD ZERO) and there is no Check engine light on either.Could it be something as simple as a vaccum line off? I've had the car for about ten years and the only engine mods is the Cold air intake I put on 7 years ago, but I keep the Cone Filter like new. Any Help will be much appriciated, Thanks