No, after a couple weeks, temperature won't help anymore, too late now. Two things could have happened:
A) You might have used the wrong kind of yeast. Some "hefeweizen" yeasts are for the American style, not the Bavarian. The American style ferments very clean, while the Bavarian/German style is the one you want for clove, banana and bubblegum.
B) You might have overpitched. Bavarian hefeweizen is a rare case when you want to stress out the yeast on purpose by underpitching by about 75% on purpose in order to get more of those lovely clove and banana flavors. If you followed Mr. Malty calculator or equivalent, your beer will turn out too clean.
Fix one or both of those, and you'll do a lot better next time. Try WLP380, that's a good one for sure, but it does need to be stressed out or it's too clean.