NO SPEAK ENGLAISH!!!

No big difference. You always miss the point. The point here is about "be doing" and "do".

1) I wonder if you could do me a favor. 2) I was wondering if you could do you a favor. Which one is correct? When I learned English I was told to use the (1). But I heard many people when they asking for help, they use (2). Is (2) better than (1)? Why? Maybe the reason is that (2) is for SPOKEN ENGLISH, (1) is for WRITTEN ENGLISH. Maybe the most of people are too lazy to finish the correct English phrase, for example instead of one long phrase "For a long time I was wondering why there is I win instead of I won. I met such usage in a lot of games and movies" they tell for short: "I was wondering why there is I win instead of I won. Yeah!"