P0305, AWD failure, and loss of cruise control

HMan_Rainier

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Dec 1, 2021
29
Maine
Hi folks, I've got a few things going on in my 2005 Rainier 4.2 AWD 110,000mi and I am wondering if they are related due to their timing. Long post here - sorry.
For a few months I've had an occasional CEL (not flashing) for a misfire on cylinder 5, the car isn't riding noticeably rough, but if I'm outside of the car I can somewhat here that something is wrong. Turning it off and back on seems to fix it and if I clear the code the light stays off for a few weeks. I also occasionally lose cruise control (related?) and again if I stop the car and turn it back on it works again. This has been happening sporadically for a few months too. Annoying but not majorly problematic.

Then, this weekend after getting my emissions tested (which I passed) I was turning into my driveway and the AWD system engaged and stayed locked on. At the same time the car ran really rough and the P0305 code came back on. I turned the car off in the street and sat for a second before turning it back on. The engine ran okay, but the AWD was still engaged.
After some forum searches I figured the encoder motor on the transfer case went. Pulled mine off and fuse 8 and sure enough AWD disengaged. Installed a new one the next day and AWD stayed disengaged (no real way to test if it will engage like it should). I did disconnect the battery for 30min after the swap.

However now when I start the car the service AWD light comes on. If I drive a decent distance and then turn the car off and on the light goes off, but if I leave it parked for a while and start it the light is back on. Additionally, I am losing my cruise control much more frequently now - about 50% of the time, it always starts working again if I stop and restart the car.
My leading thought right now is a possible bad ground somewhere, but I really am at a loss. Any insight or help would be greatly appreciated.
Thanks
 

mrrsm

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Any time you spot a *Flashing CEL* ...that means the P0305 Problem needs direct attention much sooner than later. THIS Thread covers a LOT of ground on how to investigate this issue. The AWD issue is probably NOT involved with the P0305 problem...which is much more critical right now:

Part 1:


Part 2:

 

HMan_Rainier

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Dec 1, 2021
29
Maine
Thanks for the quick reply. I haven't seen a flashing CEL yet. Just steady burn for the P0305, and that stays off for a few weeks eaxh time I clear it. And it's not riding like other cars I've been in when they were misfiring and they buck like crazy.
I did read that thread last night and checked the battery connection and all the grounds I could find. They all seemed good to me.
The problem seems to come up most often after prolonged idling, but that may just be a coincidence. I think it's possible (maybe likely) that it's happening all the time just not enough to trigger the CEL most of the time.
 

mrrsm

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(1) Try Swapping the Suspect #5 Coil Pack with any of the OTHER Coil Packs to eliminate any issues with over-heated Primary Coil Side and if you can see that the Coil Over Plug "Ribbed Metal Radiator" on top is a Different Color... then DO NOT TOUCH IT unless you want the Tips of your Fingers Burned Off.

NOTE:

The EFI Spraying or Atomizing Fuel during the Intake Stroke affects the performance of the Spark Plugs in ways that if CONSTANTLY LEAN CONDITIONS ARE PRESENT... then the involved Coil Pack(s) will DIE trying to function properly in a Lean Atmosphere while trying to Create a Better Spark Firing UNDER THE STRAIN felt during Secondary Ignition Spark Sequence of Firing that can Damage or Destroy the Coil Over Plug (COP) as covered in the Link mentioned in Item (3) below.

(2) Again... The Same Idea applies here ... But THIS Time... Swap an Adjacent Spark Plug and see if the problem MOVES from the Suspect #5 Cylinder to the New Spot.

DO NOT REMOVE ANY SPARK PLUGS UNLESS THE ENGINE IS ICE COLD. JUST READ THE 'WARNING' MOLDED INTO THE TOP OF THE VALVE COVER!

(3) Spend some time perusing THIS ENTIRE Thread to get some additional Ideas on How to Use an Inexpensive Oscilloscope to examine what is happening INSIDE of all the Cylinders to view the "Coil Over Plug Ignition Parade". Likewise, the "O" Scope allows you to view ALL of the EFI's Wave Forms performing as a "Parade". Then you can find out whether or not the #5 EFI is the Real Problem.

Trust Me... THESE Oscilloscope Diagnostic Methods, Information and Instructional Steps are GOLDEN in situations like THIS one.:


Oh... And if the Engine Falters due to Misfires... That alone may be enough for the PCM to sense a problem ...and Kick Off the Cruise Control.
 
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HMan_Rainier

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Dec 1, 2021
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Maine
Thanks for all the insight.
The #5 coil did not look any different from the others. I did swap it to see if that would make any difference. Engine is hot so I didn't mess with the spark plugs - I can try that later. All of the plugs are newer with only about 12000mi on them.
I read through the Oscilloscope thread - I definitely see the value there. Unfortunately those are going to be out of my price range for a few weeks until my summer job starts.
 
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mrrsm

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Paul "Scanner" Danner takes us through an Early Model GM Product throwing a P0300 Code... and pins down the problem to a *Stuck CLOSED* Fuel Injector. Watch THIS Video to see what the "O" Scope brings along and he will demonstrate its use in finding a BAD EFI:


Take Note... When Paul Snapped the Throttle... He placed the Engine Under Load and Stressed the Ignition Spark. And because there is a Malfunctioning EFI in the #5 Cylinder... The Spark Plug was *trying* to Bridge the Gap on the Electrode... with NO Fuel and Air Mixture under Compression to HELP via the presence of SQUEEZED Hydro-Carbon Molecules. The Result? A Repeat Misfire that can only be cured by an R&R of the #5 EFI and if NOT... it will certainly Overheat the Coil and BURN IT OUT::

SNAPTHROTTLEIGNITIONPARADE.jpg
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
I went through the exact same thing for the misfire.


Never was able to figure it out. I just don't idle it much. Haven't checked the misfire counts lately.

For the AWD light, you will need a scanner capable of scanning more than just powertrain codes. I'd recommend an ELM 327 Bluetooth OBD adapter and the Chevrosys (free) or Car Gauge Pro ($) apps on Android. The problem may be a wiring or TCCM issue. Getting the actual code may help pinpoint to the problem before throwing more parts at it.
 
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HMan_Rainier

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Dec 1, 2021
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Maine
That's an interesting thread. Hopefully I'm in the same boat.
Do you think it's worth getting a compression test to rule out valves?

I just ordered the OBD scanner you recommended. It's supposed to arrive Monday. I'll post what I find when I get it.
 

Chickenhawk

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Dec 6, 2011
779
You say you had the plugs replaced recently? What plugs did you use? The 4.2 is very picky about plugs and the ONLY ones that work are the AC Delco 41-103 iridium plug. Any other brand will cause misfires.

If you used the 41-103 plugs but changed them recently, the coil is now suspect. If they are not seated exactly perfectly, they can burn out, History of this site shows a lot of owners started having a bad coil shortly after changing plugs. The suggestion above to swap the coils is a good one to nail down a bad coil pack.

As for the cruise, it is probably not related to the misfires unless your light starts flashing. On our platform, most cruise problems that go away after a restart are the brake light switch.
 
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HMan_Rainier

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I had the plugs done at a shop for its 100k tune up. Asked them to use the 41-103 but never verified they did. Is there a way I can check by pulling the plugs and looking at them?

Another thing that may be worth mentioning is that the car can be bouncy at idle or when I'm cruising at a consistent RPM. Its not really violent, more like a steady shake/bounce. It's felt like that the whole time I've owned it. But after reading some misfire threads I'm wondering if that's a symptom. It felt like it before it threw a code, but it's possible it's gotten worse recently - hard to say.
 

mrrsm

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By coincidence...THIS Thread was recently revived about "Counterfeit Spark Plugs" and is Chock Full of information, still images and videos to help with sorting yours out:

 

HMan_Rainier

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Thanks folks. That's good stuff.
I should have a chance to pull the plugs this afternoon and check. Figures crossed that's all it is.
 
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mrrsm

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Just to round off the issue of using an "O" Scope... The first recognition is that while it may seem a bit pricey as a Diagnostic Tool... in ALL of these situations of guessing "What IS Really Wrong Here...?" (Coil Over Plugs, EFIs AND the Relative Compression Test) they are ALL Completely Non-Invasive, Passive Diagnostics... Grease & Wrench FREE... :>)

These should be Saved in every Mechanic's "Known GOOD vs. Known BAD Wave Form Library" because sometimes, these distinctions of What to LOOK for ...can be VERY Subtle:

Known BAD EFI Wave Form (NO 'Pintle Hump' Present):
KNOWNBADEFIWAVEFORM1.jpg

Known GOOD EFI Wave Form ('Pintle Hump' IS Present):
KNOWNGOODEFIWAVEFORM1.jpg

Another Example of a "Known GOOD EFI Wave Form" followed by an Explanation of all the Electrical On Screen Artifacts:

8ulr42B-2251675922.jpeg

4220617231_c41860904b_b.jpg

As for using a "Relative Compression Test" all you would need in addition to the "O" Scope is a High Amperage Clamp fitted around either the B+ Power Cable or the Negative Ground Cable leading to The Starter. Then Crank the Engine over for 5-10 Seconds and view the Initial Amperage Draw as a HUGE Spike due to Counter-Electro-Motive Force until the Electrical Pattern levels out and appears across the Screen and a series of sharp Peaks and Valleys.

If any of the Cylinders are NOT sealing and producing Compression Resistance... the Pattern for THAT Cylinder will show up as having a Minimal Amperage Draw Spike and reveal whether or not the #5 Cylinder actually has a problem with the Valves Sealing properly. Of course it then makes sense to Follow Up with a Dry-Wet In-Cylinder Compression Test to confirm whether or not the Intake or the Exhaust Valves are the Culprits.

THIS is what a "Known BAD Relative Compression Wave Form SHOULD Look Like":

blog-Options-for-testing-Relative-Compression-Pico-Screen.jpg


From Paul (and his Brother James at his Own Shop) Here are The "Scanner" Danner Brothers at work performing a Relative Compression Test AC Coupled ...BUT in this instance... They are using the BATTERY Terminals to take readings instead of using a High Amp Current Clamp tucked around either the Red Positive Cable or the Negative Battery Cable:


And in this Video, the VOP (Video Original Poster) shows the General Procedures in action, regardless of Make-Model or Engine Displacement or what type of "O" Scope is involved:


You coiuld spend an entire afternoon using In Cylinder Compression Test Equipment on this Dude's Trcuk V-8 ...OR... Using an Oscilloscope... Quickly Identify that THIS Motor has a Blown Head Gasket on Bank #2. Pretty Nifty... Always Handy!
 
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c good

Member
Dec 8, 2011
526
(1) Try Swapping the Suspect #5 Coil Pack with any of the OTHER Coil Packs to eliminate any issues with over-heated Primary Coil Side and if you can see that the Coil Over Plug "Ribbed Metal Radiator" on top is a Different Color... then DO NOT TOUCH IT unless you want the Tips of your Fingers Burned Off.

NOTE:

The EFI Spraying or Atomizing Fuel during the Intake Stroke affects the performance of the Spark Plugs in ways that if CONSTANTLY LEAN CONDITIONS ARE PRESENT... then the involved Coil Pack(s) will DIE trying to function properly in a Lean Atmosphere while trying to Create a Better Spark Firing UNDER THE STRAIN felt during Secondary Ignition Spark Sequence of Firing that can Damage or Destroy the Coil Over Plug (COP) as covered in the Link mentioned in Item (3) below.

(2) Again... The Same Idea applies here ... But THIS Time... Swap an Adjacent Spark Plug and see if the problem MOVES from the Suspect #5 Cylinder to the New Spot.

DO NOT REMOVE ANY SPARK PLUGS UNLESS THE ENGINE IS ICE COLD. JUST READ THE 'WARNING' MOLDED INTO THE TOP OF THE VALVE COVER!

(3) Spend some time perusing THIS ENTIRE Thread to get some additional Ideas on How to Use an Inexpensive Oscilloscope to examine what is happening INSIDE of all the Cylinders to view the "Coil Over Plug Ignition Parade". Likewise, the "O" Scope allows you to view ALL of the EFI's Wave Forms performing as a "Parade". Then you can find out whether or not the #5 EFI is the Real Problem.

Trust Me... THESE Oscilloscope Diagnostic Methods, Information and Instructional Steps are GOLDEN in situations like THIS one.:


Oh... And if the Engine Falters due to Misfires... That alone may be enough for the PCM to sense a problem ...and Kick Off the Cruise Control.
 

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mrrsm

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EDIT: June 11th, 2023

THIS Is @c good 's On Topic Thread involving a SHORTED OUT COIL OVER PLUG...t hat got HOT enough on top to BURN his Fingers:


@c good ... When I was describing this event, I thought about what happened to you personally a while back... but I wasn't sure if I rendered THIS precise of an explanation in connection with your Thread explaining WHY it had happened... (No sense in Adding Insult...to Injury..)

It follows though that I did NOT want to offend or embarrass you by name, either. THAT was a very unfortunate accidental event. Nonetheless, these Weird Atmospheric Combustion Chamber vs. Secondary Ignition Principles involved here DO apply to your earlier circumstances as well. And I Thank You for Bearing Witness to this Danger. Please... Drop a Link to THAT Thread here, if you would care to do so since it is SPOT ON.

THIS is Important:

The Lesson here is that IF you find a Sketchy or Shorted Coil... **** to Look for Carbon Traces inside the Rubber Boot and along the Spark Plug Ceramic Insulator. The ACTUAL issue here is that once the Secondary Ignition Spark Firing Line "Climbs The Ladder" trying to Bridge The Gap... it can cause Very High Voltage Oscillations that can back propagate and SEEK GROUND by working their way back into the Primary Coil section and hence create the Terrible Increase in the TEMPERATURE that can lead to the Failure of the Coil On Plug...and perhaps... Burned Fingers.

Eventually... Any One Single Failed Coil CAN Short Out and prevent the SUV from even Starting. Remember... it is the LEAN CONDITIONS that need to be sorted out, too... So just replacing the Damaged Coil with a Brand New One will NOT solve the problem of having a "Dry Cylinder" caused by these LEAN CONDITIONS without knowing whether or not the EFI in the #5 Cylinder is really Failing. Burned Out Coils are a SIDE EFFECT of this Problem... NOT its CAUSE.

**** Avoid re-using the COP Rubber Spark Plug Boots and Old Contact Springs
 
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Chickenhawk

Member
Dec 6, 2011
779
Yes, this is sounding more like a coil problem, provided the plugs are 41-103.

Most of us have used the Delphi coil with good results. Be SURE you have seated the coil over the plug correctly, as the main cause of coil failure besides age is incorrectly seating them, causing premature failure.

Once you get that sorted out, work on the cruise problem. If it works correctly, it was because the truck detected misfires and disabled the cruise. If it still doesn't work until you restart the truck (common problem) then replace the brake light switch.

The problem with the brake light switch is that there three different contact points inside, and unless you have a Tech 2, it is hard to diagnose. But it is inexpensive and easy to change.
 

HMan_Rainier

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Dec 1, 2021
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Maine
I'm hopeful that it's just plugs or coils. But I am starting to get worried about valves. The light is so infrequent (every few weeks) that it's hard to know if anything is making a difference. I swapped the #5 coil with a Delphi one off a wreaked H3. It hasn't thrown a code yet, but it is still bouncy at idle or constant RPM - which I'm now assuming is a symptom of a misfire.
I should be able to pull the plugs to verify those are good this afternoon.
And a new OBD scanner arrives Monday which should be able to see misfires even if they are not throwing a code.
 
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TollKeeper

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Almost sounds like a computer clear, and throttle body cleaning is needed..

Dont forget to check to make sure the PCV hose is securely fastened to the intake resonator, as it can cause un-metered air, and cause havoc.
 

HMan_Rainier

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Maine
I'll check the intake PCV when I check the spark plugs.
Would a fouled throttle body affect just one cylinder?
How would I go about getting the computer cleared?
 

TollKeeper

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For the throttle body, its an easy process.. But I would read up on the throttle body cleaning.

I Know theres a detailed thread about it somewhere around here, but I am mobile at the moment, and cant search.

Basically, while your doing the throttle body cleaning, you leave your battery disconnected. Its the only computer clear by battery disconnect that still works on the modern cars and trucks.,
 

HMan_Rainier

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I'll add throttle body cleaning to the reading list. I have came across that on here before.
I had the battery disconnected for a good bit doing the AWD - so that should have reset the computer.
 

TollKeeper

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You will find we only recommend using the ACDelco plugs on these trucks.
 
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HMan_Rainier

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Yeah - I have read that. I also saw someone saying that NGK makes the ACDelco ones too.
I quick search only returned positive experiences with the NGK.
Still worth changing?
 

TollKeeper

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NGK/NTK Makes the O2 Sensors, not heard the one about spark plugs, and cant find any supporting info about it.

Worth Replacing.. I never tell another person how to spend there money! :smile:
 

HMan_Rainier

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Maine
Well I'm about to eat my words 😂.

Made my last post after pulling just the #2 plug (easiest to reach) decide to pull #5 too (misfiring) and found this.

I'm certainly not a spark plug expert, but could something like that be causing my problems?
 

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TollKeeper

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Most Definitely.. Electricity will always follow the path of least resistance.
 

HMan_Rainier

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Maine
Makes sense to me.
Should I be concerned about what caused the plug to do that? Or is it just bad luck and the wrong plugs.
 

TollKeeper

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I am just hoping that all the porcelain came out when you pulled the plug, and none made its way into the cylinder.
 

Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
Just to be sure, I'd replace all of them with 41-103. And who knows where those came from. If from evilbay or Amazon, they could be fakes, which is maybe why it broke.

Counterfeit ACDelco Plugs
On top of that, from what I see on RA, they're the wrong ones. Should be LTR5AHX

 

HMan_Rainier

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Dec 1, 2021
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Maine
Update:
Replaced all 6 plugs. Idled for a few minutes and went for a 20min drive on back roads.
It's definitely running smoother, but there is still some sort of shake/shutter/bounce about twice a second. I think it may have become less severe - hard to say.

Found some interesting (potentially concerning?) things when I switched the plugs.
The plug on #5 was broken see pictures above.
The plug on #3 was covered in oil (see picture), mostly on the threads but also on the top of the plug and a bit on the bottom of the coil. I did notice this coil was the loosest to unscrew and I was able to move it alittle from the top before unscrewing it.
The plug and coil on #6 was very corroded (see pictures). There was some liquid on the walls around the coil which I wiped down. I'm pretty sure it was water - it didn't have any smell or color.
 

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Mooseman

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Oil and/or water in the plug well is caused by a leaking valve cover gasket. You could try to compress it a little more at the plug coils by adding a washer under each of the bolt heads for the coils. They do unscrew from the coils. If that doesn't work, then a new valve cover gaskets set is required. Don't go ape on those bolts as they can break in the head.
 
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Chickenhawk

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Dec 6, 2011
779
Sounds like you are working through multiple problems. We are big believers in looking at the most common problems first, and there is a good reason why we say that genuine 41-103 plugs are the only ones that seem to consistently work.

Because you disconnected the battery, you also need to clean the throttle body. This is so common that we almost put it into our signatures - there is no PCV valve and the computer 'adapts' to a gummed-up throttle body over time, but as soon as you disconnect the battery, the PCM loses its adaptation settings.

A 'bouncy' engine feeling can also be worn motor mounts.

Once you clear all your codes, see if the misfire still comes back. If it does even with new plugs, it is probably the coil.

If the cruise works, great. If it still doesn't work until after a restart, consider replacing the brake light switch.

As far as the bit of oil or water in the plug area, I wouldn't worry about it too much. Most of us have that and they still work fine. If the corrosion seems to be the worst in plug #4, you can add some weatherstripping to the hood seal to prevent rain water from dripping onto that particular coil.
 

mrrsm

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Use some caution with "editing" the Tightness of the Threaded Rod-Bolt on the COP (Coil Over Plug) Coil Packs because the length of the threaded portion screwing inside the Aluminum Engine Head is only M6 X1.00 X 12mm ***AND*** they have a STOP LEDGE and thus... WILL Snap the Threaded Portion... RTF Off.... if the Tightening Torque should exceed 87 Inch Pounds. So... *Tighteners* BEWARE!

Also... If you were NOT able to retrieve the Fractured Portion of the White Ceramic Insulator that fell from the Spark Plug... You might consider using a Bore-Scope to investigate whether or not that Ceramic Fragment fell down inside the Cylinder and is either waiting to do ( or hopefully has NOT done) any of its Mischief to the Delicate Edges of the Four Valves inside ...or easily score the Chilled Cast Iron Cylinder Wall and Top of the Piston.

Echoing @Mooseman from Post #37... The other source for that moisture is likely coming from the Flattened Out Rubber "O" Ring Style Gaskets in between the Valve Cover and the Head, allowing Post-Combustion Blow-By Gas and Steam to come through from Engine Combustion Blow-By pressuring under the Valve Cover... and then later condensing after the engine cools down. It seems like it might be the time for changing THESE:


ACDELCOVALVECOVERGASKETKIT.jpg
 
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HMan_Rainier

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Dec 1, 2021
29
Maine
The spark plug stayed together until I took it out of the socket (not over the engine) so I'm not too worried about that.

What does changing the valve cover gasket entail? Is there away to check to see if that is actually the problem before replacing it?
 
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