Spark Plug rethread 01 LC

[Ahimsa]

Hi Guys,

Recent addition to the IH8Mud forum. So CEL came on and it sounded like a bad coil. Got the autoparts store to read the code and sure enough, misfire cylinder 5. Bought coil and new plugs. Here is the kicker: took out the coil, started to pull the spark plug and it was loose!. Kept turning it and thought damn its completely stripped out, literally came right out. The engine has about 90K on it and from the look of it (and the grime encrusted coil) it has been like that a long time. Furthermore the rest of the plugs all looked original (including the one I pulled, all denso plugs). So I buy a kit, rethread the hole and put in a sleeve for the new plug. Working fine. So I am wondering if these ARE original plugs, I bought this used about two months ago and have been going through it making sure its mechanically sound (I will also post a thread on the timing belt replacement).

Here is my question: How did the plug get stripped out? I can think of a few alternatives...if someone replaced the plugs, but I don't think they did, so did it happen at the factory? Anyway, I just wanted to post this as an interesting story. Once I get it figured out I will post some pics of the process in the event someone can benefit from it.

Cheers!

 

[PADDO]

FWIW original factory plugs *may* have a letter embossed on the top of their terminal nut, at least my factory fitted originals did and their identical part number iridium replacements did not. A few others have mentioned their factory installled plugs had letters on the terminal nuts too.

 

[Ahimsa]

Hah very interesting. They are embossed with the letter P.......hmmmm

 

[Ahimsa]

it does make me wonder what would cause that. either overtightening at the factory or something else. pretty amazing it wasn't found in 89K miles!

 

[JayM]

I had original plugs that were loose also. I think this allows carbon build up in the threads over time and then you go to wrench it out and the treads can come with it. Had the same discoloration on the coil boot as well. Seems the factory may have a torque issue. I've heard of different plug manufactures on one side of the motor to the other. Small price to pay for a bombproof v8.