Map Scrolling in 2007 M35x

[KGBhoy]

Does anyone know how to navigate the map slowly? Usually when you're on the map and hit right/left/etc. you move in blocks. Sometimes my system would allow me to scroll slowly instead of jumping by block. But I can't figure out what this depends on - I tried zooming in all the way, or zooming out a little, and those things don't work.
Anyone knows?