2008 aveo 1.6 not idling

[chevaveo1.6ls]

hi there all my dads 2008 aveo 1.6 keeps on dying at stop streets and robots.there is no fault codes coming up,we have changed the idle air control,but still the same.car starts up straight away no struggling.but sometimes die straight away or it will idle.other times it will go for a day or 2 without problems.dont know what more to check.any help will really be appreciated.could it be coil,dont want to change it just for a hunce because they are expensive.

[chevaveo1.6ls]

hi there guys if it is a vacuum leak will it be like that the whole time or can it be intermittent as well