what,s wrong
 

my 85 rx-7 wont idle it runs and drives fine it just wont idle

First check the big vacuum hose near the back of the intake manifold on the pass. side.It gets cooked by the exhaust heat and often splits,causing bad idle problems.
If its just idling too low and not actually miss-firing,you can turn up the idle speed with a flat screwdriver.Its hard to see,but its there.If you stand on the drivers side and face the engine,the screw is near the back of the carb,facing straight towards you,under all the linkage and crap thats attached to the rear of the carb.
Its not the screw near the bottom/center of the carb,by all the vacuum hoses facing diagonally up.Thats the idle mixture screw.That will also affect the idle,but you shouldnt mess with it unless the engine is missing or sputtering badly.If it is,then you can turn it out a little at a time to richen the mixture.For setting idle from scratch on a modded or replacement carb,you usually turn the idle mix screw out untill the idle stops speeding up(usually about 900RPMs).Then you adjust the speed screw out until you get about 750-800 RPMs.
If playing with the speed screw doesnt help,try the mixture screw,but do it in small increments and note where you started, so you dont get all lost and end up worse off.
BTW,it could also be weak ignition.Idle quality is most affected when plugs,wires or coils are bad.

most likely a vacuum leak. Spray carb cleaner or starting fluid around the engine bay while its running ( requires 2 people). If your rpms go up when u spray in a certain area you have found your leak.