Just bought this 2006 Mazda 3 s with 2.3 and 5sd auto with option manual shift and it usually at slow acceleration at 40 mph the car vibrates or shudders it does this til you get to approx 45 mph then it stops rpm's doesn't seem to matter. If you accelerate fairly quick and pass thru 40 to 45 quickly it never does it only when accelerating slow and steady. Please any suggestions would be very helpful .

Car has 127000 miles on it.

 

Has no one seen this before?

 

It may be your engine mount going bad. Mine did. There is a TSB out on it.

 

Did you ever figure out what this was? I'm having the same problem!