So earlier today I was forced to park in a dirt lot. The entrance is covered in gravel and has a bit of a slope.

Leaving, I bottomed out and ended up scraping for a few seconds (slow speed). Since then, I've been getting a few weird weird noises.

There's a droning/humming sound (best I can describe it, almost sounds like wheel bearings) that seems to be RPM based. It seems like it only occurs at 1750, 2250, and 3000 RPMs.

When starting cold, there's also a rattling sound that almost sounds as if something is loose and rattling around in the front side of my car. This doesn't happen with warm starts.

The sound itself sounds like it's coming from somewhere around the dash to the back of the engine bay. I'm not able to lift my car to check it out, but I didn't notice anything weird taking a peek underneath.

The thing that confuses me the most is that it only happens at certain RPMs.

Any ideas on what could be causing this? I'm going to have it checked out by a shop on Friday, but I'd like to know what to expect in advance.

 

The exhaust is the lowest point on the car. I've bottomed out quite a few times. The cats and Y pipe are flattened a little and the W brace has a couple dings in it.

The rattling is probably gravel trapped on top of the tray under the engine.

I don't know of anything that would cause your other sounds though. Maybe someone else has experience.

 

Plastic parts are probably torn

 

+1.

 

I've ripped off my under body plastics before on my winter car. And I heard a scraping sound much like yours. But it wasn't rpm dependent.

 

That's the thing that scares me.

I'll try to get a better look today and see if I can find any torn parts.

 

Took a look underneath, looks like I might have broken a small plastic piece, but I don't think it's a big deal, and I don't think it has anything to do with the sound.

I did some aggressive accelerations and threw out a few rocks. The sound is less frequent/non-existent now, so I'm guessing that's what the problem is.