Bad O2 sensor?

AntrimMan

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RC you need to get a visual down the plug wells before and after blowing out the puddled oil. A cheapo flex scope on a smart phone from a black friday sale. A piece off a broken plastic clip or other errant object falling down the well onto the plug and coming to rest at the hex portion would stop a plug socket from seating. Get calm. Start with the easy things. Gather evidence before drawing conclusions.
All the best.
 

RCinNC

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A good idea, AntrimMan. To my discredit, a borescope hadn't occurred to me. I found one for my cellphone on Amazon.

I went back out this morning and after multiple frustrating attempts, I managed to get this photo with my non-borescoped phone:



Here's a blowup:



Now, I'm not sure what I'm seeing here. It almost looks like a couple pieces of wire, or a piece of a spring clip, or something. I can't dislodge it with compressed air (though my only source of compressed air is the canned type). My magnetic probes are too large. I tried to magnetize a piece of steel wire, but either it wasn't strong enough or else that isn't ferrous metal. My precision forceps aren't long enough to be able to get to the bottom of the well and still be able to manipulate them. I'm going to have to go look for a really long pair of precision needlenose pliers.

Does anyone else see what I'm seeing?
 

JJTJ2

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I bet trying to get the socket on the spark plug just wedged it down more. Could you get an old coat hanger and see if you could get under it and try to flip it up so 1) it is no longer lodged in there and 2) something you have might be able to snag it.
 

RCinNC

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I bet trying to get the socket on the spark plug just wedged it down more. Could you get an old coat hanger and see if you could get under it and try to flip it up so 1) it is no longer lodged in there and 2) something you have might be able to snag it.
I've been giving that a go, both with a section of coat hanger and with a selection of different shaped picks that I have, but so far it's a no go. I think I'm gonna have to find (or make) a tool that can actually grab whatever is in there (if there is actually something there) and pull it out.

This has been a very good lesson for me. I cleaned the oil out of the spark plug wells before I pulled the plugs, and blew them out with compressed air, and still it's possible that something remained in the plug well. It's probably a good thing that whatever debris might be in that hole actually prevented me from getting a socket on it; if the debris was smaller and I was able to get a socket in there, it's very possible that in spite of taking precautions, something still could have fallen through the hole into the cylinder.

Thanks to AntrimMan's suggestion, a borescope is going to become part of my toolbox. I will never pull plugs again, even after I've blown the plug wells out, until I physically look deep into the well to make sure it's clear.
 

RCinNC

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That's similar to one of the ones I've tried. The problem is that I can't really see down into the spark plug well, so I'm flying blind, and I'm not sure the hook is even able to grab ahold of whatever might be there. I have a borescope on the way from Amazon, and the borescope has a hook attachment that might be useful. I also ordered an alligator hemostat, that has very small thin jaws that'll hopefully fit down between the spark plug and the wall of the spark plug well and let me actually grab ahold of what might be in there.

And tomorrow I'm heading down to buy an actual air compressor so I can get a decent amount of air into the spark plug wells and blow out whatever might be stuck in there.

One way or another, if there actually is some sort of debris in there that's blocking the socket, it's coming out.
 

AntrimMan

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RC, yes I do see what you are seeing in the non-borescoped pictures. Would I be surprised if it was of a rubbery consistency normally used to seal oil in that has slipped out of place during installation? No I wouldn't. But rather than jump to conclusions why don't you tell us what you have found it to be.
All the best.
 

RCinNC

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Well, once I bought one of these:


And one of these:


And one of these:


I was able to find this:


Sorry for the grainy quality of the photo, I had to take a picture of the screen with my phone.

After I soaked down the spark plug well with brake fluid, I was able to suck out all the oil/brake fluid mix with a Mity Vac, at which point I could finally see something jammed between the facet on the spark plug and the wall of the spark plug well. I couldn't dislodge it with a pick or with compressed air from the compresser, but I was able to get a grip on it with the alligator hemostat and work it out of its position.

And here it is....


It appears to be a very sharp piece of gravel that wedged itself into that space like a piece of a jigsaw puzzle. Without the borescope and the alligator hemostat, I'd have never been able to see it clearly, or been able to remove it; even the compressed air wasn't getting it loose. At least I have the tools now to be able to get a good look down into the spark plug wells before I remove the spark plugs.

And tomorrow I can go back to square one. I'll pull all the plugs again so I can look inside the cylinders and make sure that nothing manged to fall into one of them when the shop had the plugs out and the valve cover off the last time. I'll finally be able to pull plug #3 and see what shape it's in. A valve clearance check is waiting on a new valve cover gasket.
 

Fennellg

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Freakish rare event. Made me think of all those old f150 spark plugs that use to break. It may have been easier to brake the plug. But you did not know what you were dealing with.

Nice job. You stayed on it and prevailed



:)
 

RCinNC

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I don't think that even breaking the plug would have helped; even with the entire insulator gone, I still wouldn't have been able to get a socket onto the plug's hex. Shame on me, Fennellg, for not thinking that there was something stuck down in the well that was jamming up the plug. Based on the way it felt when I was trying to get the plug socket on it, it just felt like the facets on the plug were too big and weren't fitting into the socket. It was a refresher course in not jumping to conclusions. I guess that even if I did figure is was a piece of debris stuck down there, I'd still have had to jump through all the hoops I did; there's no way I would have ever even been able to clearly see that rock, let alone remove it, without the tools I had to acquire.
 

Fennellg

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Not sure this would not have frustrated a seasoned mechanic. Wonder if Tobasco has ever bumped into anything like this?
 

RCinNC

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If I had to guess, that rock must have fallen into the spark plug well after the shop installed the gasket and valve cover and reinstalled the spark plug. Maybe it was stuck to the valve cover and got knocked loose. If it fell in before the plug was installed, it would have either fallen into the cylinder, or else it would have ended up on the bottom of the plug well and they wouldn't have been able to get a socket in there to tighten the plug.

I'm almost afraid to pull the plugs out again and look into the cylinders with the scope. The Ark of the Covenant is probably stuck in one of them.
 

Cycledude

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Couple years ago a rock similar to that got jammed next to the steering head and almost caused me to tip over, luckily I was nearly stopped when it happened.
 

AntrimMan

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RC, it's nice to "see" you are making progress. Not the strangest thing I ever saw though.
A spark plug stuck in my daughters car tire caused a flat.
Twenty five years later her boy beat that with a pair of slip joint pliers in his car tire.
I do wish the oxygen sensor is the culprit you are searching for after all this.
All the best.
 

cyclemike4

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O.K. this really is useless information and doesn't help RCinNC at all but here is my spark plug story. I had a truck years ago that had the pollution pump taken off. the tube that came out of the intake was pinched off and soldered shut. It rotted out and the truck would not run. So I thought i would just take the fitting out of the intake and put a plug in. Easy right? Well I put a cheater bar on dad's strong arm and thought I was going to turn the truck over! I wound up breaking dads strong arm. So I looked around there was a old spark plug laying there. It looked about the right size for the hole and the soft tube was still inside the fitting. I put silicone around the plug threads and just turned it straight down into the tube. It seated well and didn't leak. I had a spark plug sticking straight up out of the intake in front of my carburetor. I am lucky none of my a$$ buddies didn't move a spark plug wire to it while i was not looking to see what it would do. haha. that plug stayed in there for over 100,000 miles and was still in there when i got rid of the truck. I would forget about it because i was so used to seeing it when i would open the hood and some one would see it and ask what the heck is that. I would tell them it is a 9 cylinder motor and that spark plug wire fell off.
 

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Not sure this would not have frustrated a seasoned mechanic. Wonder if Tobasco has ever bumped into anything like this?
In my life- yes……. (Old school engines, totally different design) Tenere - no.
How would that even get in there? Really strange situation for sure.
 

RCinNC

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In my life- yes……. (Old school engines, totally different design) Tenere - no.
How would that even get in there? Really strange situation for sure.
It's perplexing to me too. It couldn't have been there before I changed the plugs, back when I first noticed the valve cover gasket leaking back in March 2024, . If it had been there then, I'd have had this problem way back then. So it's safe to say that plug well #3 was stone-free when I buttoned everything up before I took it to the shop for the valve gasket replacement in May 2024. If by some circumstance the stone had fallen into the plug well immediately after I finished installing the plugs in March, then the shop would have caught it in May and they would have had to remove it themselves in order to do the job, and it wouldn't have been there when I pulled the plugs a few days ago. So it must have found its way into plug well #3 while it was in the shop, after they'd installed the spark plug but before they installed the coil stick.

As soon as I get them downloaded, I'll post photos of the spark plugs. I didn't see anything remarkable about them, but someone might have a different opinion. Unfortunately I couldn't get a look at the inside of the cylinders; the camera head on the scope was too big to fit through the spark plug hole.
 
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RCinNC

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Here are the photos I took of the spark plugs. Does anything about their appearance look unusual?






The one other thing I found while examining the coils was that there was some damage to the end of Coil #3. It looked like this:


This is the damaged coil next to an undamaged one for comparison:
 
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