Idle vibrations and sometimes stalls (rare though)

Car vibrates on idle most of the time, however once in awhile the idle is perfect usually if the weather is very hot, so I do not think it is the engine mounts. I have also added fuel injection clearer and the Idle goes from rough to smooth, but I have only done it once. Idle vibration is annoying! The car stalls are super rare, like twice a year, I have had the car for two years.