Same issue, with "je viens (pour) sauver ton chat", where I was marked wrong for omitting "pour".
Over on that thread, Sitesurf responds:
"Venir" is one of these verbs that do not need a preposition to introduce an infinitive.
There is a tiny difference in meaning if you add "pour" before the infinitive:
- If you use "je viens pour sauver ton chat" you express your reason for coming: you will try to save the cat, no success guaranteed.
- If you use "je viens sauver ton chat" you express the end goal of your action; you mean to save the cat.
Because in this case the pronoun "les" expresses a direct object. Indeed, "Ils/elles" are used as subjects; "leur" for indirect objects (i.e. "I speak to them = Je leur parle", singular: "lui"); "eux/elles" for indirect objects with prepositions (i.e. "He leaves with them = Il parte avec eux/elles", singular: "lui/elle"). http://french.about.com/od/grammar/a/pronouns.htm
That's "venir de":
Technically it's not exactly incorrect, but it's quite unusual.
When we add a gerund after "come", usually it's part of a phrase indicating the manner of the arrival. For example: "a little robot comes barging in"; "the tree came crashing down".
On the other hand, "a little robot comes, saving them" (with a necessary comma) would mean that the robot's arrival itself is what saves them.
"A little robot comes to save them" indicates the purpose of the robot's coming.
By the way, in English we don't put a space before a question mark (or any two-part punctuation mark, unlike in French).
That is--or perhaps was; it might be old-fashioned--a rule in France; a lot of the books I have that were published in France put the space in, and my wife's old grammar books (published in France, but used in Canada) have the rule, but with her notes that they're not to do that as it's not done in Québec French.