You might try checking what the existing values are:

>>> rcParams['axes.formatter.limits']
[-7, 7]

and try:

rcParams['axes.formatter.limits']=[-4,4]

Sorry, I didn't check the current values :|
It works like a charm now, thanks for all the helpfull answers :)

Matthieu
--
French PhD student
Website : http://matthieu-brucher.developpez.com/
Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92
LinkedIn : http://www.linkedin.com/in/matthieubrucher