It is pronounced [일리리] as Hyejeong says (it seems Hyejeong is always right :-). This is a little tricky because it would normally be [이리리] according to the liaison principle, since ㅇ follows ㄹ. For example, phonetically it is the same case as 일이 많다, which is pronounced [이리만타]. The reason it is pronounced [일리리] is because it is a compound word - both 일 in it represent an independent word 일 (task, matter). So each 일 is pronounced with emphasis on it, which turns off the liaison and makes it [일리리]. This happens quite often because in Korean, words are constantly combining together to form new compound words. For example the dictionary lists 먼일(먼 앞날의 일) as a noun, but it comes from "먼 일" (adjective + noun). People don't care about whether it has become a new compound word or not, and pronounce it as [먼닐] as if 일 is an independent word. In other words, the normal liaison you see in words like 일어나다 generally happens in a single word only, For multiple words or compound words, each one tends to be pronounced as an independent unit because people put emphasis on it separately. This is similar to some English compound words retaining stress on each of the original component. It can be difficult to know the correct pronunciation in all these different cases. But when in doubt we can always consult the dictionary as most dictionaries show such special pronunciations. For example, 네이버 국어사전 lists 일일이 pronunciation "[일리리]" at http://krdic.naver.com/search.nhn?dic_where=krdic&query;=%EC%9D%BC%EC%9D%BC%EC%9D%B4. Anyway, one doesn't need to be overly concerned with such pronunciations because people will still understand you even if you get it wrong. No need to be too afraid to speak freely because of them.

Please don't use English romanization, it's anything but close to the actual Korean pronunciation. 일일이 is pronounced 일리리 [illiri].

일일이 is pronounced like 일일이, which, because of the natural carryover of sound, sounds like 이리리. (Though I see Hyejeong says it's 일리리) It does not and never will sound like any Romanized spelling.