Lately I've noticed that when I start my engine after it hasn't been running for a few hours regardless of temperature, it runs with a really low-pitch sound and kind of loud. It didn't do that when new. I asked about it before on the old forums but everyone told me it was normal and to ignore it. Well, i did but now when I drive off "low-pitched" and come to a stop my car starts jerking a little. Also, when I pull off, it acts as if it doesn't want to go(almost like it's about to stall out but it's automatic). When I get a little way down the street it stopps and everything goes back to normal but is quite embarrassing. Is this normal??