Hi again,

Thanks for the post back this is good information. So it runs good and smooth with adequate power when up to normal hot.
You mentioned it's take awhile to warm up and that could be a lazy or not completely closing thermostat. If you are using anything but a Wahler thermostat this can happen rather regularly. I have found that the other brands are not as reliable for as long as the Wahler. For a few dollars more I have better success. The Wahler put a manufacturing date on theirs. I had one two last so long I took it out out of fear and another after 17 years. It broke open. One of its bracket legs just gave out from fatigue.

What you are describing now is that it is running lean. If this were a 1989 or newer you would probably be getting an engine trouble light and code for rich/lean mixture, of which, tells you nothing but to go hunting! So with the ' 84 you are not having to deal with that mess of inconvience.

I need to ask a guestion about when you start the car or more like before this happened. With your foot off the gas, does or did the engine hit and then race upward and settle back down to an idle? I gather it's not doing that now but did it back before this issue started?
If the IACV does respond like the above example this is the normal operation and the Valve is good.
Keep this in the back of your mind for a routine pre-drive check off list.

There are a several ways to get this "lean" condition. I would start with the simplest cause first which is getting excessive air behind the AMM.
The first place that this can happen, besides rotten vacuum hoses, is in the accordion tube between the AMM and the throttle plate.
You need to undo the ends and pull it off. Take a bright light bulb and run it up inside and flex the hose to reveal any cracks or splits.
As the engine moves it can rub spots on the top edges and crack down between the volutes. The hose does stiff and the wiggling first starts out as an occasion dying episode or a case of temporary idle shuffles.

By checking this item it removes a possible fluctuation of air or mixture imbalance that upsets the computer in how it controls the Idle Air Control Valve.
You could remove the IACV for a cleaning and testing, if you think, it's not working at this time.
Check all the hoses connecting to the large hose at the two side ports. The ports can have a circular crack at the base point too.

You do mention that it does not idle well. This "Could be a hint or clue" that helps me decide to start simple.

Keep your eyes open for anything odd that I have not mention like a loose clamp or some wiring issues as a good maintenance opportunity. The 1984 has a history of engine wiring harness issues and its doubtful it hasn't already been addressed in some way by now.

Phil