I have a 1990 Honda Accord EX with 222,000 miles on it. I was attempting to change the PCV valve and found that the grommet was cracked and falling apart. While removing it from the engine, a small piece about half the size of a dime, fell in. It's disappeared down there. I am wondering if this could ruin something or if it will be OK to leave it in there... Thank for any help!

 

I'd pull the valve cover and see if you can get it/find it. Something about a piece of rubber floating around in the engine/oil doesn't make me sleep well at night.

 

Yes, I would get it out. It could potentially lodge between the springs or possibly clog or partly clog and oil drain port.