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Plug in my old Sable blew out after a few thousand miles. Coil on plug design. Heli coil fix lasted over 100k miles. I got that car used at 80k from my wife's job fleet. Looked like OEM plugs were in it.
In the fleet Chevy vans from my retired from job they left plugs in those 4.3 motors until they started misfiring in the 150k to 180k range. Damp weather or the onset of winter was the trigger.
 

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2011 Equinox 1LT V6 3.0L FWD 174.6k miles
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…in my research the past few days, I found some recommendations to pull the plugs while motor was still warm, and then install them after it was completely cool…
…I also think my #5 plug issue may have been a factory defect…there really wasn’t a lot of carbon build up on the plug, but that bottom 1/4” was sure stripped…which brings me back to my next question: there’s an inch of threads on each plug, does the hole in the head also have an inch of threads, or is this thing just in with about a 1/4” of damaged threads?
I would think the threading would match on both (for maximum hold). Otherwise they'd just thread the very lowest part of the plug ... like a long bolt that has to pass through something but can only fasten at the very end.

But looking at your damaged plug ... it almost looks like the the damaged threads are "fused" ... and even "flattened"?.

It doesn't seem like cross-threading alone would've caused that kind of damage (to the plug) ... maybe to the Head, though.

Almost seems like the damage occurred after the plug was installed, making it very difficult to turn it out later.

Could those threads have been subjected to extreme heat, which caused them to melt, distort, or "fuse" together like that ? Is that known to happen?

And if so, would this be a failure of the plug to withstand the heat it was designed for, or could it be indicative of a cooling problem in the Head?

Also - I wonder about that Head now ... forcing those "melted", "fused", or "flattened" threads all the way out the Head's threaded hole! Every single one of those female threads must've gotten "mushed" by those "vague" threads on the way out!.

And then what (??) ... they got "re-cut" by the new Plug going back in?

Now I'm wondering ... is this how plugs eventually "blow out" ...
 

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I would think the threading would match on both (for maximum hold). Otherwise they'd just thread the very lowest part of the plug ... like a long bolt that has to pass through something but can only fasten at the very end.

But looking at your damaged plug ... it almost looks like the the damaged threads are "fused" ... and even "flattened"?.

It doesn't seem like cross-threading alone would've caused that kind of damage (to the plug) ... maybe to the Head, though.

Almost seems like the damage occurred after the plug was installed, making it very difficult to turn it out later.

Could those threads have been subjected to extreme heat, which caused them to melt, distort, or "fuse" together like that ? Is that known to happen?

And if so, would this be a failure of the plug to withstand the heat it was designed for, or could it be indicative of a cooling problem in the Head?

Also - I wonder about that Head now ... forcing those "melted", "fused", or "flattened" threads all the way out the Head's threaded hole! Every single one of those female threads must've gotten "mushed" by those "vague" threads on the way out!.

And then what (??) ... they got "re-cut" by the new Plug going back in?

Now I'm wondering ... is this how plugs eventually "blow out" ...
All good questions. As far as the damaged plug, it’s possible it could have been carbon buildup that caused that problem, but I can say that getting that plug out damaged all of the threads in the head on the way out. I initially started to use one of the old plugs try and clean up the threads in the head, but I couldn’t even get it to start until I put some force on it. After getting it down a thread or 2 with some force, I pulled it back out because it was so difficult to get it started. I then thought well the damage is done, so I might was well just crank down on the new spark plug and just get it installed. It took the same 18” ratchet to get enough leverage on it to get in as it did to get the original out. I’m confident it’s in there good, but one of 2 things will happen at the next plug change…it’ll be so fused it won’t come out at all, or it’ll completely strip the head on its way out and leave nothing for a new plug to grab onto leaving a helicoil or something as the only option.

I’m hoping the new plug may have cut some new threads on the way in leaving it in there securely…
 

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…I can report that after 120 miles, these E3 plugs provide the smoothest idle I can recall in my Equinox…granted, it may just be having new plugs in general, but she’s got a very smooth idle…
 

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Just did a 400 mile trip…I saw an increase in mpg’s with E3 plugs…granted once again that it could just be the fact that they’re just new plugs, but running cruise at 80 mph, I actually saw 25.5 mpg’s at one point in my DIC. I normally get 23.2-23.9 mpg’s on the old plugs…600 miles total since the E3’s were installed with damaged threads on cylinder 5…
 

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They are not a platinum or iridium center electrode plug so be ready to replace them around 30-40k miles if that.
They are snake oil, just like the Bosch multi electrode plugs. Right up there with mechanic in a bottle.
New plugs always run good at first installation compared to worn out ones.
 

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2011 Equinox 1LT V6 3.0L FWD 174.6k miles
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Was talking with a co-worker today about this plug situation and he mentioned another situation with Ford plugs 'breaking off'?

So I did a quick search and found this story:


If you read down toward the middle, it says something like ... [paraphrased]: "if you haven't changed the original plugs prior to 80,000 miles or so, and they're not mis-firing or otherwise throwing codes ...just leave them in there ... because they're probably fused to the cylinder head at this point and will break off when you try to remove them!!

"But those factory original plugs can go 140,000 miles and more (!!!) .especially if the vehicle sees more highway driving ... which keeps the plugs cleaner"

====

So that's my situation ... except I'll be crossing 176,000 shortly on my original factory plugs!

My 2011 3.0L engine has made at least (11 x 2) + 4 ... 900-mile one-way trips so far ... so that's 23,400 miles X 2 = 46,800 miles where it was run HOT for, on average, 14.5 hours continuously.

Maybe this is why these plugs have lasted this long?
 

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2022 Equinox RS AWD, 1.5T, Iron Gray Metallic, Build Date 12/10/21 Purchased 12/17/21
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Why does that matter? Does the tapered seat versus the gasket make them more likely to get stuck in there? Or are you just saying the tapered ones are more likely to leak (and this could become a problem on #5)?
In a past life (about 30 to 50 years ago) I was a mechanic and I hated changing plugs with tapered seats. They seem to fuse onto the heads and were almost always a pain to remove. I saw a higher percentage of stripped and/or broken plugs that were tapered compared to plugs with gaskets. Just my personal observation from a couple decades experience.

Changing tapered plugs when the engine is good and warm does help. Of course until you get the intake off it will cool down a lot.

All that said, I changed the plugs on my 2013 3.6 around 220,000km if memory serves (@140,000 miles) and I had no issue removing the plugs. No pentrating oil or other aids needed. I did have the engine good and hot so by the time I got the intake off it was still pretty warm. The only issue I had was one the bolts on the rear valve cover broke off - it held a coil pack in place. The wiring harness for the coil pack was so tight I just put it back together and wasn't worried about the coil pack working loose, and it didn't to the day I traded it in at 347,000km.

I never had a drop off in power or mileage the entire time I had the car, changing the plugs didn't help or hurt things. The plugs I removed looked almost as good as the new ones - I did use the OEM iridium plugs since they worked so well for so long. The valves were nice and clean, surprising so. From reading things here I expected some carbon, but I was doing almost exclusively highway driving and the old Nox really seemed to enjoy it. It treated me well, I do miss the old buggy.
 

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I had a '07 4.6 Mustang GT with the 2-piece plugs. Bought it new and I changed out the plugs at 10k miles to a one-piece plug. Only Champion made one-piece plugs at the time vs Autolite factory welded together 2-piece ones.
Sold it at 35k miles. Well known issue with those motors as it's a long plug with an extended reach past the threads that it a smooth snug fitting extension through the head into the chamber.
 

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They are not a platinum or iridium center electrode plug so be ready to replace them around 30-40k miles if that.
They are snake oil, just like the Bosch multi electrode plugs. Right up there with mechanic in a bottle.
New plugs always run good at first installation compared to worn out ones.
A new C8 Corvette is on my radar…30-40K miles is long enough to hold me until then 😁
 

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A new C8 Corvette is on my radar…30-40K miles is long enough to hold me until then 😁
What's that gonna set you back (???) ... $75k ????
 

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What's that gonna set you back (???) ... $75k ????
Base C8 does 0-60 in 2.9 secs.! You can get one at sticker if you order from one of the top 3 Corvette dealers. Base is all I want, so $63K and that’s a bargain vs any other car with its capabilities! I’ve always wanted one, but when the C8 went mid-engine, it made my next car list! I’m divorced, daughter is graduating, don’t need a family car anymore, so it’s time!
 

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Just got back from FL. The shuddering is much worse. 99% sure it’s still a misfire, but still hasn’t set off the CEL light…I just ordered all new coils…
I’d have cruise set at just about any speed, the misfire would happen, I’d lose a mph, engine would increase revs and then I’d gain a mph, then it’d settle back to what the cruise was set on. I was able to watch the tach and speedometer both jump for the 3 secs or so the shudder happened…
 

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@BandDirector : I hope you’re right! I think we’re in the same boat and I’m headed for the same thing ... whatever it is.
 

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I think if you are seeing the tach jump the shudder is the transmission. Is there a downshift in there?


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If I increase revs, it goes away…even without a downshift. It isn’t downshifting to stop the shudder. Usually happens around 2K rpms, but I’ve seen it at as little as 1600 rpms…
 

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My D in L '16 3.6 AWD 'nox is in the dealer now. 77k miles.
Trans was hard downshifting when coming to a stop, braking or coasting. There is a TSB on sticking valves in the valve body. They changed the valve body but still a hard downshift is happening. Looks like a reman trans is going into it.
Warranty Co. approved inspection for debris and the valve body. Waiting for final approval for trans. replacement on last call from dealer on Fri. afternoon.
Ally warranty, service manager doesn't see any issue with them approving trans replacement. I've got a good dealer and relationship with them, and service is upfront with me as he knows I'm a motorhead. It got a driver's side window actuator also as it was weak rolling up.
 

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I just went on a test drive with a scanner hooked up. No codes, no pending codes. It also didn’t do the shudder on the test drive. So if I take it to get looked at, the same thing may happen, so at this point I guess I just have to wait for it to get worse so it can be diagnosed…
…I’m beginning to think I may have a tranny or torque converter issue. Auto’s are beyond my scope of knowledge, so taking it to be looked at is all I can do…
 

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@BandDirector : but is your Scanner going to pick up Transmission Codes? I thought you needed a “professional” Scanner to be able to do that ... either at the Dealer, or an Independent with one of those (more sophisticated) SnapOn units...
 
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