There are no glaciers in September infact u will have to struggle hard to spot any snow on mountains 
Rainy season is also usually over so muddy patches and nallahs will be less and it is much easier for cars to reach Babusar pass. A few pages back in this thread, someone posted pics of Babusar pass in July and u can see so many vehicles already there. In Sep, it will be much easier.
But only trouble may be the occasional rain which can happen anytime.
But again, please visit in daytime. Another incident of snatching happened with campers at Jalkhad recently.