Car sat for a week. Just started it up, it's about 50 some degrees here and I noticed after idle kicked down to it's final resting place of about 700 rpm's when I would just barely touch the gas pedal and bring tach up as it hit 1000 a harsh vibration was felt and you could also hear a difference. Although once warmed up and driven it's gone. But I never noticed this before. Anyone elses do this??