I may have found the source of the misfire

TollKeeper

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Dec 3, 2011
8,047
Brighton, CO
One of these things is not like the other.. Sorry, first thing that came to mind.
20210416_145236.jpg
Samples from Spark Plugs (13) in the Periodic Table


I have seen worse thou.. From a DSM
destroyed spark plug - engine is toast? | DSMtuners.com
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Could have been defective and the ground wire fell off. Usually it's the center electrode that is gone.
 
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6716

Original poster
Member
Jul 24, 2012
821
I'm having all kinds of fun. The #3 plug is super stubborn, I've been slowly working it back and forth while doing the other plugs, still stuck.

And then I over tightened the #1 coil bolt and it snapped but fortunately left just enough above the hole to let me get a needle nose on it.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
That's why antiseize is your friend. Also make sure you pull the plugs on a cold engine.
 
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6716

Original poster
Member
Jul 24, 2012
821
Engine is cold. All other plugs are swapped. Can't remember if I used the anti-seize last time but I am for sure this time. Had to ask three times at the parts store for anti-sieze, he kept handing me dielectric grease for the coil boot.
 

6716

Original poster
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Jul 24, 2012
821
5 out of 6 ain't bad? I'm tempted to leave that one in there. There's 70k miles on these, the other plugs that came out looked ok.

I just can't tell that I'm making any progress. It moves, like I get maybe a couple of quarter-turns on it.

But yeah.
 

JayArr

Member
Sep 24, 2018
504
Mission BC Canada
Did you change them last time? It may not have been changed last time either.

I'd leave it alone until I had the Helicoil set to repair the threads when it comes out or you may be without a vehicle.
 
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6716

Original poster
Member
Jul 24, 2012
821
Did you change them last time? It may not have been changed last time either.

I did them last time and it was for sure changed then.
 

6716

Original poster
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Jul 24, 2012
821
So if the plug doesn't come out nicely, and I force it and it all goes to heck, is my only recourse to swap the head?
 

mrrsm

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Oct 22, 2015
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No... TIME-SERT Sells Dimension Specific Spark Plug Repair Kits. Unlike using a Sketchy Heli-Coil Solution, The TIME-SERT Method allows for a Solid, Matching Threaded Steel Cylinder to be installed in place of the Stripped Out Aluminum Threads that will become a Permanent Repair and obviate the need for the Drastic Engine Head R&R:

https://www.timesert.com/html/sparkplug.html


...and a "Hands On" General Application Demo of How the TIME=SERT System vs. The Heli-Coil System works:



I have had considerable, successful experience with using this Repair Method on the GM 4.2L Engine; such as Replacing Stripped Out Coil On Plug Fastener in the Engine Head and Replacing a Stripped Out Head Bolt Fastener Hole in the GM 4.2L Engine Block, all well documented along with other applications here at GMT Nation. So I can Testify that the TIME-SERT Thread Repair System... REALLY DOES WORK!

GM 4.2L Engine Head Coil On Plug Stripped Out Thread Fastener Hole Replacement using the TIME-SERT Method:


GM 4.2L Custom High Performance Engine Block TIME-SERT Mains Steel Thread Line Inserts Upgrade:

 
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mrrsm

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I'll stress the need for examining the submerged GM Atlas 4, 5 & 6 Cylinder Engines Deep COP Cavity using a 7-9 mm USB Bore-Scope with the feature of being able to visualize the positions of ALL FOUR VALVES as the Piston slowly rising upwards, Before Top Dead Center (BTDC) when ALL of those Valves SHOULD BE CLOSED.

Also... While achieving this condition, the Piston Head should be WELL BELOW the reach of the TIME-SERT Tools as they will need to enter into the Upper Combustion Chamber to first, properly cut in New Threads and then to ensure that the NEW TIME-SERT Spark Plug Insert is SECURELY LOCKED IN PLACE using the Lubricated Insert Delivery Tool.

Having the Piston located at least 1" to 2" below that position on its BTDC Rise is very important, as the Upper Cylinder will eventually need to be Cleaned Out with Compressed Air and then Checked that No Aluminum Dross is left inside of the Cylinder or can Escape Around any Open Valves.

You can accomplish this by first establishing TDC on the #1 Piston using the linked Extra Long TDC Tool and after Reading the Engine Firing Order right off of the Plainly Embossed-Imprinted Valve Cover, gradually Rotate the Engine By Hand, ONLY in a Clockwise Direction using the TTY Crankshaft-Harmonic Balancer Bolt with a Socket and a Ratcheting Breaker Bar very gradually until the Involved Cylinder being worked on achieves the Correct "Closed Valves - Piston Rising BTDC" condition BEFORE beginning this Repair.

Innova used to sell the Longer Version of this Tool, but nonetheless, this is still the Most Accurate Method of confirming TDC of the #1 Piston on its Compression Stroke:


INNOVA7880TDCTOOL.jpg
 

flyboy2610

Member
Aug 24, 2021
460
Lincoln, Ne.
To reduce the amount of chips you have to remove, thoroughly pack the flutes of the drill and tap with grease. Pull them out of the hole frequently and clean them, also.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I have to say that I haven't heard of a plug getting stuck, broken or threads buggered up on these engines even though I have had some that were really tight and "cracked" when they broke free and complained (squeaked) all the way out. If they are original, they shouldn't have been over torqued.

I have only had one plug ever give me a problem and that was on a late 80's Olds Quad 4. It stripped the threads in the head on the way out. I was able to fix it with a Help! type kit that came with inserts, a tap and thread locker.
 

mrrsm

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Oct 22, 2015
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Apparently, the GM Atlas Engineers under Mr. Ron Kociba back in the Late 1990's realized that THIS would become a serious problem of having "dissimilar metals" fighting each other whenever the LL8 Engines were at or near Operating Temperatures and the Aluminum Engine Head Thread Lines were coming out ...right along with the Spark Plugs if removed under High Temp Conditions.

So they Opted to emboss a "Permanent Warning" along the edge of the Valve Cover for Owner's & Mechanics NOT to Remove the Plugs until the Engine Cooled down. They also included the Correct Installation Torque in both Newton Meters (18) nM and Foot Pounds (13) Ft Lbs ... along with listing the Engine Firing Order, too (153624):

VALVECOVERWARNING.jpg
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
I concur that I have always removed them on a cold engine.
 
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mrrsm

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I was just ‘Thinking’… Perhaps an Easier and Just as Effective Method to perform this required Inner Cylinder Components Arrangement would be to Use the Hose and the 14mm Spark-Plug Hole Adapter from any of the Compression Tester Kits available via Amazon...

https://www.amazon.com/14mm-compression-tester/s?k=14mm+compression+tester

Then... while Slowly Hand Cranking the Motor Over… Place your Thumb over the Pneumatic Adapter End ... and Wait for the Air Pressure to Rise and Hiss loudly. This would alert you that All Four Valves have Closed and that the Piston is Definitely on its way upwards for its Compression Stroke… EZ – PZ.

COMPRESSIONTESTERHOSE1.jpg
 

6716

Original poster
Member
Jul 24, 2012
821
I have to say that I haven't heard of a plug getting stuck, broken or threads buggered up on these engines even though I have had some that were really tight and "cracked" when they broke free and complained (squeaked) all the way out. If they are original, they shouldn't have been over torqued.
I replaced them myself the last time.

I appreciate your experience on this, my big concern is that I have a tendency to apply too much force and break stuff (even when I know I am prone to doing this). So I wanted to make sure I had a backup plan if I applied too much force here and broke something.
 
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6716

Original poster
Member
Jul 24, 2012
821
Finally got this stubborn plug taken care of. It still had 16,000 miles on its service interval so I wasn't in a rush but still it needed to be done.

I brought it to a shop that has done good work and treated me right on a couple of things I would have done myself if I had a garage right now, but I don't.

They quoted $250, then charged me only $145 when they didn't need to use the e-z out. Which is a lot for one plug, but a lot less than the anxiety, tools, and time I would have sunk in if it went wrong if I tried it.
 

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