1991 Honda Civic plug removal

I just bought a 91 Honda Civic DX. I want to change the plugs, i have a 5/8" socket, it fits the replacement plugs. I can get the socket down the valve cover tube, but there is a (rubber?) gasket or something covering the metal part of the plug. I can see the white insulator part, but some black ring is preventing the socket from getting to the metal part of the plug. all 4 cylinders are the same. I replaced the valve cover gaskets to hopefully get a clue, but that did not reveal anything.

Does anyone have any ideas what I am doing wrong or what might be preventing me from getting the plug removed?

Thanks!

A WAG: Sometimes, equivalent plugs of different brands take different size sockets. See if a 3/4 or 13/16 socket does the job.

That black stuff might be baked hard oil. Oil sometimes seeps down to the bottom of the tube and if it stays long enough, heat from the engine and metal of the plug could bake the oil into a solid or semi-solid.

You could try using a long screwdriver and see if you can chip it free.

Are they all like that? If its just one plug, it might be the rubber grabber thing from inside your spark plug socket.

I am pretty sure its the 5/8" socket. Its the only one I can get down the hole.
I will double check that though.

Yes, all 4 cylinders have it. At first, I thought it came off the spark plug wire harness.
I cannot prove it didn’t. I tried to hook into it with a wire, but could not grab it.

I will see if I can do anything with a screw driver.

THANKS for the feedback!

So after the replies, I checked with a screwdriver and found that it is rubber. I then crafted a hook from a coathanger and was able to snag
the pieces. It looks like a rubber boot from the end of the plug wire. what i think happened is, the valve cover gasket was bad and it leaked oil into
the spark plug tube area, then, after sitting for ever in a pool of oil, the rubber plug from the bottom of the boot, just slipped off.

Thanks again for your replies!