One problem you could face is...a chunk of hard carbon crust could cut through the aluminum treads when removing the plug. causing what you would call "cross tread" that is the main course, not installers fault if its cross treaded.

get a couple of cans of carby & throttle body cleaner. remove the intake pipe to T/B, hold the revs at 2000rpm & spray two cans in there.

2 cans?? isn't that a bit excessive?

I had an EB XR6 come in once, 2 of the plugs were seized, one was that tight that i was rooted by the time i got it out, the other i got the rattle gun onto it, took me around 30 mins of hammering and it finally came out, f**k was almost glowing it was that hot.
As soon as i got it out it was clear that water had played the part and severely corroded the plug, i took the head off and a lot of the water jackets were badly corroded, so bad it went right through to the valve seat.
I took the head down to my mate and he repaired it, i was close to throwing it away but he done a top job, that was 3 or 4 years ago and it's still going ok now.

see the shiny bit of thread at the tip. thats aluminum torn off by hard carbon on spark plug that was left on to long. seized up & also cross threaded the threads on the cylinder head.

a bit excessive alright

clean it from the intake side. that will make removing alot easier or consider the other possibility mentioned by WALKER above.

 

 

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hey guys thanks for all the tips,

hey Slick, what did you mean cleaning it from the intake side (sorry bit mechanically illiterate lol)

spray carby/throttle body cleaner into throttle body. read my previous post at the beginning. it'll soften the hard carbon build up a bit.

ah true thanks mate ill give it a go

I think your head gasket is cracked