2913 Mazda 3 vibration at idle (misfire?)

[steve333]

Hey all,
I have a new 2013 Mazda 3i Sport Sedan Automatic
When warm at a red light the engine has a vibration that feels like a misfire (an intermittent shudder).
The dealer says it is normal (like they always do) but can this really be normal on a brand new car?
Thanks for any opinions.

 

[steve333]

Tach normally at 750.
If I drive on the freeway or drive ober 55 on the street, when I come to a stop at a red light the tach drops to a little above 500, sometimes it seems like it will stall but doesn't.
I've never had a car that varies at all. The Cobalt was at 800 every single time.