The Nissan Path

I have recently replaced a Nissan Pathfinder 2006 engine with the new good one used the engine. After three months now I am going to replace the spark plug.

I have successfully replaced the 5 spark plug but when I have tried to no 3 plugs and I have inserted the plug tool in the slot but the tool not going up to the plug. Then I have noticed that there is a metal sleeve in the slot.

Can anybody assist me what is the purpose of this metal sleeve in the spark plug slot?

How I can remove that metal sleeve to change the spark plug.

Thanks

What engine are you working on? If it's a VQ40DE, the sleeve would be the spark plug tube and it is pressed into the top of the head. It's purpose is to keep the oil out of the spark plug well and it is sealed at the top with a seal built into the valve cover. If your tool doesn't fit down the spark plug tube, you may need to find a more narrow spark plug socket.