Sometimes when I accelerate from a stop, I hear a sound coming from underneath my car. It's almost like a fluttering sound. I can only hear it with my windows down. I think it's only around mid throttle. I haven't had any problems. Anyone know what it could be?

 

It depends....are all your windows down? Or are only the fronts down or only the rears down?

I've found that it creates some type of vacuum (sounds like a helicopter) and only is evident between 30-45 MPH.

Next time that happens, look around to see which windows are down. After you notice which window is down, bring the opposite windows down (ie- two front windows down -> chopper sound -> bring down rears).

Good luck!

 

It might be a leaky gasket between the exhaust pipes. I remember my dad's V8 made a similar "fluttering" type sound on acceleration and it turned out to be a worn out exhaust gasket between the pipes near the tranny. It was really easy to replace.

My car makes that sound too but I haven't taken the time yet to check it out. It's really doesn't bother me because it's barely noticeable and I hear absolutely nothing when my windows are closed.

 

Had a similar situation. Lexus dealer put car on the rack and found a plate that protects the underbody from exhaust heat had come loose. Replaced it for free.