My son's 88 RX7 had a surging idle. Well, maybe not really surging, but sometimes it would idle OK about 750rpm. Then it would go down to about 300rpm and die sometimes. It had a little surging or lumpiness to it (I think that's the correct description).

I adjusted a screw inside a black plastic shroud between the passenger front strut tower and the air filter box. It seemed to help, but I wonder if this is a long-term fix...or a correct fix for this problem.

Here is a video of what it did before I adjusted that screw. You can hear the idle surge, then a puff of something, then repeat.

https://dl.dropboxusercontent.com/u/...102529_664.mp4

 

you adjusted the idle mixture, which is part of the idle adjustment procedure, but i'm not sure if it will fix the problem

the shop manual Foxed.ca - Mazda RX-7 Manuals has a whole page on how to set the idle, its probably the best place to start.