There is a really great guy in Oakville near the Go Station. I am not sure what the name of the shop is. You cannot miss it. He will be able to diagnose what the problem is without costing too much.
I take my BMW 740i to BK Motors in Waterloo as I had bad experiences with both Mississauga BMW and Budds. BK Waterloo are the best service department and honest. I trust them.