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Different size diameter spark

373 Views 5 Replies 4 Participants Last post by  dfb399
So I’m having this issues where these spark plugs are the same part number and everything but if you look closely at the thread diameter one is thicker than the other. The thicker diameter spark plug only threads into one cylinder while the thinner one would thread to all other 3 , idk I’m new to the automotive world and I just need help I’ve been looking everywhere for the specific plug but had no success
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D16y7 auto
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Looks like you have an insert attached to the plug
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Looks like you have an insert attached to the plug
What’s that? Sorry new to everything lol

It was just that! A plug insert thank you!
thread repair insert.
Easy way to spot it is the notches in the upper thread, that's to lock it. You probably wanna add some locktite to that and reinsert it, allowing it to cure before putting plug back in and restarting.
Spot on, it is definitely a Repair insert, that has backed out with the plug when you removed it.

I would NOT do any "re-inserting", unless you are educated and well-practiced at Time-Sert Spark plug thread repair, in which case you wouldn't have created this thread..
There is a kit worth of tooling needed to install these properly, including a cutting tool to cut a new Spot-face for the crush washer to seal against.
Furtherly, there are Insert Install/Removal tools for properly installing them, so this does not happen again next Plug change.

I just went through this on my Y7 last week, ended up pulling the head and taking it to the Machine shop that performed the repair 1st time around.
They fixed it free of charge (as they should have).
They did inform me, pulling the head was not necessary for the repair, but it made more logistic sense for me to leave them the head rather than the entire car.

Good luck.

I'll make one exception: You could try threading that same Plug/Insert combo, right back in (make sure you know which cylinder, for obvious reasons).
Snug it by hand, Torque to 156 In./lbs., and see if it holds (Tq. value came straight from my FSM).
It likely will, but alas, you are stuck with a 'used' plug, until it is fixed correctly.
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