[Buffalo4]

If they actually did do a compression test, then, THEY caused this problem. What were the compression reading they gave you?
ie, You CANNOT do a compression test in cylinder where the hole is blocked.
It cannot be part of the spark plug socket insert BECAUSE the spark plug was REMOVED!!
An insert sometimes gets stuck to the spark plug insulator, not stuck in the threaded hole.
The coil is the same.

And YES, a better photo could actually help.
If the OP didn't put anything into that hole after he removed the spark plug, then?????
C'mon guys???
Buffalo4

 

[Buffalo4]

I did the same (zoom in). That has a hex head shape and tapers upward ... @white2015 , I'm pretty sure you're right: its the darn rubber thingy that is inside a generic spark plug socket. I've had them fall out (luckily with the socket not over the engine's spark plug tube.)

@bresodyssey , what was the result of all this?

OF

Well then, how did they do a compression test? Can they use an adapter that doesn't screw into the spark plug hole threads?
After the compression test the OP tried to install the spark plugs and found the hole plugged up.
Unless he put his spark plug wrench into that hole BEFORE he put a spark plug in his wrench, I don't understand how that obstruction happened. Still, the helpful suggestions on how to remove, whatever it is, are good.
it will be interesting to see what it is and 'how' and 'when' it happened.
Some info definitely seems to be missing.
Buffalo4
PS: I guess that while he was installing sparkplugs in the adjacent cyls the rubber plug may have dropped out of the socket and into the hole. I would think he would have realized that when he put the spark plug in the socket to do that cyl, as it wouldn't stay in the socket without that rubber plug. 🤯

 

[Buffalo4]

Might even try to figure out how to blow it out with compression of the engine??
Seal any hole in it with a long 'bolt' or dowel, etc. Course, not responsible for any damage to engine or person!!! 😈

 

[Buffalo4]

If compression in that cylinder would blow it out it would have come out long ago.........

Not if there is a hole in that plug. I would bet that if you crank the engine over now a lot or air comes out of that hole. Does it? Course you don't want to take the chance of it getting sucked in.
Is it possible that the plug was in the hole and you pushed it into the spark plug threaded hole while attempting to put in a new plug?
Either way, you need to get it out. Maybe even use a long lag type bolt that will screw into that rubber plug, or whatever it is and it might be able to pull it out, A left handed thread would be best, if they even make such a thing.

QUESTION? Did the mechanic do the compression test in his shop? If so, how did you get the Ody back to your place?
Buffalo4

 

[Buffalo4]

Funny thing, my magnetic spark plug socket is a bit to strong so it can pull out my extension if I'm not careful... still much better than the rubber insert style. Its also a good idea to hit the spark plug ceramic with just a bit of dielectric grease / silicone lube to allow the spark plug boot to pop out easy the next time.

-Charlie

GEARWRENCH 3/8" Drive 6 Pt. 5/8" x 6" Magnetic Swivel Spark Plug Socket - 80546 $10.88 on Amazon now.
That's what I have. The 6" extension is not removeable from the socket. But, if you add an additional extension, it could pull out. Very handy and less than $15.
And I also use the dielectric grease.
Buffalo4

 

[Buffalo4]

And the 'plug' did not look like it even got down deep enough to get into the threads.
But, hell, it was interesting and entertaining. 🤣
Buffalo4

 

[Buffalo4]

Damn, I was really messed up as I thought that the hexhead 'block' in the lower 'hole' was what the problem was. .
I just mistakenly jumped to the conclusion that the obvious spark plug in upper hole was NOT the problem since I could easily see it was a spark plug. A clear photo would have been much better along with a description or circle around the problem area.
The good news is that the problem is fixed and that the threads in that spark plug hole are OK.
Just drive it as normal until the muzzler arrives and enjoy it.
And thanks for the excellent update!!
Buffalo4

 

[Buffalo4]