Burnt spark plug coil

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Tlhfirelion

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(Pics attached).

Hello. 2008 Honda Pilot SE, AWD. 166,000 miles. We recently bought this and it runs fine but I am doing basic maintenance. I changed out the plugs and found them and the coils all looked good except for one. The front and center plug and coil on this 6 cylinder looked burnt. All the other coils looked gray with no oil or anything.

The vehicle starts and runs just fine and performance is as you'd expect. I'm puzzled as to what could cause this. Anyone have any feedback? I did change the plug and am ordering a replacement coil, but I've not seen that before so figured I'd ask.

Thank you in advance for your assistance.

8023D22C-9F9D-4609-9645-619FE7C05193.webp


20A3B0CF-ACC6-4A6A-8C56-249C04FCF3DD.webp
 
I went to one heat range colder spark plug, due to ethanol in fuel...

OEM - NGK IZFR5K11
One colder - IZFR6K11
https://www.rockauto.com/en/parts/ngk,6994,spark+plug,7212
 
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I agree with Kira et al. Burnt-on oil.

At 166,000 miles on a Honda V6, you should have had an exhaust valve adjustment by now. I had mine done at over 200K and my trusted independent mechanic said the exhausts were tight, tight, tight, and the intakes were all over the place but generally within spec. If you intend to keep the vehicle, and it hasn't been done already, I recommend it. Of course you'll get a new gasket set as part of the service. My local dealer doesn't recommend this service, the Honda manual says to check it and adjust when the timing belt is done. The "check it" is almost always a pencil whipping at the dealer. Shop labor time is 3-4 hours.
 
Had something similar happen to our 06 Odyssey ~ 90k mi. Misfired & threw a CEL. I was out of town ( of course ) so my wife had it towed. Shop said a plug was loose which allowed exhaust gas to destroy the coil pack.

Incidentally, I've since seen posts at OdyClub saying that it's not uncommon for plugs to become loose on the J35's (same engine series as your Pilot) and you should periodically check them. Not sure why but maybe VCM vibration may be a factor.
 
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Looks like what happened to my 2012 Transit Connect. No CEL but engine just didnt sound the same. Called my buddy who is a Ford dealer mechanic and he immediately said to check #3 spark plug its probably loose. Well he was exactly right #3 spark plug was loose and it discolored the plug and the coil pack and there was a little bit of oil in the plug well. Took plug out and cleaned it up and tightened back to spec and tightened the couple valve cover bolts around this area and the leaking stopped and the weird noise, exhaust leak, abated. i know the exhaust gas temps has hurt the gasket around the #3 plug well so another valve cover gasket set has been ordered, a whopping $20 bucks.
 
It does look like oil residue and not actual burning of the coil. For the following reasons:

1. Look at the hex on the plug, it's also dirty (and that would be the lowest point).
2. A coil pack that got hot enough to "burn" by changing color would have destroyed the plastic/rubber first.
3. The discoloration is mostly even across some lengths of the connector, usually (but not always) a burned coil shows more damage closest to the porcelain.
4. You can almost make out the droplets that condensed closer to the top of the pack.
5. If the coil was really burned, you would have issues. If you don't have issues you don't have anything to worry about for now.

I suspect it was a little bit of oil that ended up leaking and then being burned over time which resulted in the more volatile parts depositing onto the pack. You could probably see if it is oil by rubbing it with some brake cleaner to "clean" it up.
 
Originally Posted by Kira
What's "VCM"?

Is this "J35" the same engine as in my 2000 Acura RL? I just got this car from a sibling and I have a steep learning curve to endure.




Variable Cylinder Management. Essentially turns the engine into a V-3 (maybe better, an I-3 dragging another I-3 along side it). EDIT Under circumstances of light load, etc. {end EDIT} Increases both fuel economy -- and levels of controversy on internet discussion sites.
wink.gif
Some like, some hate, some actually sell kits to deactivate it. Yes, your climb up the curve is just beginning.
 
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Originally Posted by Tlhfirelion
No misfires but that kinda stuff bugs me. "One of these things is not like the other". Lol

Elmo say careful -- Oscar the motor grouch is coming to visit. . .
 
Originally Posted by dbias
Looks like what happened to my 2012 Transit Connect. No CEL but engine just didnt sound the same. Called my buddy who is a Ford dealer mechanic and he immediately said to check #3 spark plug its probably loose. Well he was exactly right #3 spark plug was loose and it discolored the plug and the coil pack and there was a little bit of oil in the plug well. Took plug out and cleaned it up and tightened back to spec and tightened the couple valve cover bolts around this area and the leaking stopped and the weird noise, exhaust leak, abated. i know the exhaust gas temps has hurt the gasket around the #3 plug well so another valve cover gasket set has been ordered, a whopping $20 bucks.

If the plug is loose it will run hotter than a properly torqued plug.
 
If this car is fitted with VCM (if you have an eco light it does) I suspect that is the source of the problem. This would be VCM 1 which runs the front cylinders only some of the time and they run much hotter than the rears. I don't see any liquid oil which is almost always present when a plug tube seal fails on these only heavy corona staining on the plug.
To get into this a little deeper the "oil" spots could be from oil vapor that will get past the seals even when fairly new, the reason this happens is the valve cover is blocked inside and the undersized PCV can no longer vent all the crankcases gases. Post back if it has VCM and those familiar with it will go through how to remedy it.

Edit: Those coils are the ones closest to the PCV and where the most gases accumulate when its partially blocked.
 
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Always happens on cylinder 5 on these engines. Replace that coil when you change the plugs. Live your life for another 100k. Whenever a plug blows out of these motors, it is always cylinder 5.
 
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If my research is correct, the 08 pilots with all wheel drive do NOT have the vcm. I'm mostly a Toyota guy but a Honda without vcm is acceptable.
 
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