I've noticed that my rx8 when it's in drive and stopped, at like a light, the idle rpm will drop a bit and the car gets a little shaky. I have already replaced the wires, spark plugs, coils(only two because the other two have already been replaced), and the starter. While replacing one of the coils, a bolt broke and I zip-tied it on for the time being. I thought that could be it, but now it's fixed but the car still does it from time to time. Any ideas as to what is causing it.

 

You can try cleaning the MAF sensor.

 

Is the A/C on when this happens? How severe is the shake? The A/C compressor can cause the rpms to drop a bit when it kicks in.

 

Yes, the A/C is usually on. I will try and see if it does it without the A/C on. The shaking isn't that bad, it drops for a sec gets a little shakey then goes back to normal.