This happened to me last week - a "flapping" sound at certain speeds on the freeway.

Check underneath the engine and see if the plastic splash guard has come undone. Apparently the clips break easily and this is a really common problem on Fits and Civics. That splash guard is what you hear flapping. The dealer fixed mine for under $140 and it's fine now.

 

Where exactly is the noise coming from, can you tell? Could be something loose, the splash shield maybe. Check around make sure everything is snug.

 

yah, sounds like the lower shroud is missing a few pieces of its hardware.. put the car on a lift or ramps and check.
dont' stick your head under the car with just the scissors jack in the trunk!

 

86? Sure it'll go that fast. Mines regularly doing 85 for long stretches as I drive to work each day 95 miles away. Probably why I can't seem to fix the damned thing. I've had it to 97 before I puckered up. Took quite a bit of rocking back and forth to get there, but it did.




Just kidding about the rocking.

 

When this happened to me it was also my plastic cover underneath. The dealer wanted $54 dollars to put it back up or they would do it free with a $59 oil change, so I had them do the oil change. Incidentally, mine happened because I had Dunn Tire doy oil change when I had new tires put on, and they didn’t know they had to change the clips...so they didn’t and that is why mine came part way off and caused the slapping sound. It’s only a few bucks more to get the full synth at the dealer so I’ll always go there now, and not deal with the clips that aren’t reusable issue.