to do something without thinking it is very important or having much interest in it (http://dictionary.cambridge.org/dictionary/english/go-through-the-motions)

to do something because you are expected to do it and not because you want to (often in continuous tenses); to do something perfunctorily, or merely pretend to do it (http://idioms.thefreedictionary.com/go+through+the+motions)