Yeah, sounds like I have the same problem too. I got my new V2 replacement engine and it's got around 400 miles and I just noticed that the tach needle has been bouncing everytime I shift. Before the engine swap, the tach needle never bounced like that before. I would like to add too, that I smell gasoline when I'm cruising. The gasoline smell is definitely coming from the car. The clutch too feels really soft and when launching the car, there's just a little bit of lag before it picks up and goes. I would like to add that I have no mods on the car except a grounding kit. I'm definitely going to take it to the dealer and see what's going on. I'm thinking it's the clutch.

 

mine was the tach jacking up. Dealer put up a huge fight cause the tech didn't agree with what i told the service manager so in the end service manager call head tech and was advised to hook up a digital and digital did not bounce so new tach installed. I should have asked for the nismo one and paid extra

 

my car does it too sometimes...but i think it maybe your foot bouncing around on uneven surfaces...drive by wire is super sensitive.

mines only does it when im speeding on a road that isnt soo smooth

 

Im having the same problem but slightly different. it happens at low rpm. My Z is A/T and when it shifts to second or third and i let off the gas the needle will drop from about 2500 rpm down to idle rpm and bounce. It does it fairly quick. For instants when you turn the car off and the needle just drops dead to 0. Thats how fast it drops and bounces around.

it doesnt do this and higher gears. Any ideas to what this could be??

 

Thank god someone posted this. I've had this problem since I bought my Z. I searched and couldn't find anything. I never had a chance to drive another Z so I thought it was just normal.

 

Oh also my car came with a grounding kit. Do you guys have a grounding kit?

 

I dont have a grounding kit that im aware of

 

I've a tach bouncing issue me too... it happens under hard acceleration, hard shifting and/or rough roads...

Little video: Look at 0:07 and 0:13

http://www.youtube.com/watch?v=JkRAH1G3tQ4