Misfire on cylinder 8 and horror help (1 Viewer)

[Juanblzer]

So I picked up a CEL misfire on cylinder 8. Checked it out and found this and a spark plug just sitting in the hole

Had two spare coil packs so I swapped one on and picked up a new plug from autozone. When I went to thread the plug in I didn’t go crazy overtightening it. I was kind of worried it would cross thread. I then Cleared code and ran it.

It ran fine for 4 days.
On the 5th day I was driving home from work and CEL hit again.
Cylinder 8 misfire

Found the exact same thing. Melted coil pack and spark plug.

I’m pretty novice with stuff and honestly don’t know where to go. Anyone have some general thoughts on what I do next? First round

New plug after 4 days

 

[JunkCrzr89]

Oh $hit. Was first plug a Denso? Second one you put in looks like Bosch trash.

My first inclination is that cylinder is running too lean and getting so hot that it’s melting the plug because a fuel injector has failed. Likely need to scope the piston to see what the condition is on top. Hopefully the engine isn’t toast now.

 

[e9999]

Obviously, that's not great looking, but can we not use unnecessarily dire language prematurely either, please?

 

[Juanblzer]

I toyed with the idea of chasing the threads on the spark plug hole —getting another denso plug— using my backup sparkpack— clearing code — and going
But
I think it will do it again and don’t want a super hot cylinder burning up more etc. so I figured I’d post here. My local cruiser repair shop is pretty good. I’m just wanting to kind of have a plan and understanding as to what I’m getting into

 

[JunkCrzr89]

but can we not use unnecessarily dire language prematurely either, please?

 

[MountaineerLC]

My guess is that the first plug walked out and in the process the threads were damaged enough that the second plug blew out as well. You may need to find a very capable shop to install a time sert. I'd think a scope and careful diagnosis is in order.

*Spark plugs working loose is a pretty well know and documented issue.*

 

[JunkCrzr89]

My guess is that the first plug walked out and in the process the threads were damaged enough that the second plug blew out as well. You may need to find a very capable shop to install a time sert. I'd think a scope and careful diagnosis is in order.

*Spark plugs working loose is a pretty well know and documented issue.*

I don’t think a plug walking out would cause it to melt.

 

[abuck99]

^ if the threads were butchered from a previous install- over time enough combustion gas blow-by could cause that to melt- like a 2800F blow torch.

 

[e9999]

if the threads are damaged, that can be fixed. Heck, if there is a hole in the piston, that can be fixed. Although if the head threads are badly melted away it may take a better insert than your usual helicoil to seal that.

 

[awesomeissquid]

I would scope it first to get an idea of what everything looks like. You can get a cheap borescope on amazing for ~$20, or even buy a more expensive one and just return it. You will want something in the 5-8mm range. That will tell you what the threads and the cylinder looks like.

On the spark plug threads you will want to carefully look at the full 360 degrees of threads. I would recommend pulling another spark plug so you can do the same and compare what you are seeing.

Inside the cylinder you will want to have the piston at the bottom of its stroke. You will want to look at the piston head, the cylinder walls, and the 4x valves. On the top of the piston you want to ensure the surface is smooth without anything that looks like a crater or impact impression. Also the edge of the piston should mate right to the cylinder wall all the way around without any areas having a larger gap. On the cylinder walls you should see crosshatching all the way around without any, or minimal vertical scratching or polish marks. Lastly, on the valves you are looking again for impacts, for any missing pieces or gaps, and also at the color of the valves. The colors you will see can range but this will tell you how the cylinder is burning. Here is a quick guide to get you started on those: Anatomy of a Valve Failure

I don’t know what your experience is with looking at any of this stuff, so if you get confused or have questions feel free to post the scope images and we can take a look and discuss. Hopefully if is just the spark plug threads, but even if that is the case I would only recommend trying to fix it with the head removed from the engine. There is too much risk of foreign metal shavings being left in the cylinder and causing damage in the future.

 

[Juanblzer]

I would scope it first to get an idea of what everything looks like. You can get a cheap borescope on amazing for ~$20, or even buy a more expensive one and just return it. You will want something in the 5-8mm range. That will tell you what the threads and the cylinder looks like.

On the spark plug threads you will want to carefully look at the full 360 degrees of threads. I would recommend pulling another spark plug so you can do the same and compare what you are seeing.

Inside the cylinder you will want to have the piston at the bottom of its stroke. You will want to look at the piston head, the cylinder walls, and the 4x valves. On the top of the piston you want to ensure the surface is smooth without anything that looks like a crater or impact impression. Also the edge of the piston should mate right to the cylinder wall all the way around without any areas having a larger gap. On the cylinder walls you should see crosshatching all the way around without any, or minimal vertical scratching or polish marks. Lastly, on the valves you are looking again for impacts, for any missing pieces or gaps, and also at the color of the valves. The colors you will see can range but this will tell you how the cylinder is burning. Here is a quick guide to get you started on those: Anatomy of a Valve Failure

I don’t know what your experience is with looking at any of this stuff, so if you get confused or have questions feel free to post the scope images and we can take a look and discuss. Hopefully if is just the spark plug threads, but even if that is the case I would only recommend trying to fix it with the head removed from the engine. There is too much risk of foreign metal shavings being left in the cylinder and causing damage in the future.

so.... the head will need to come off pretty much no matter what? Would that allow me to check out the piston with out a borescope?

BTW thank you all for the thoughtful replies to my post. I'm trying to learn as much as possible before I dive in.

 

[2001LC]

Plug blow-out is very predictable, just bases on engine sound alone. We get what sounds like exhaust manifold leak. Combustion gasses passing spark plug threads on compression stroke, always sing out TICK TICK TICK or some say POP, POP, POP. Will hear clearest while pass near a wall, as the sound deflects back to us with window open on that side. Also when vehicle driven away from us as we stand at the curb. Putting ear to fender well, further delineating and isolating side. Tick or popping sound will speed up, with increased RPM. It's most prevalent at cold start up. When heard after engine warm up, is when it's ready to blow plug out the head.

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

I do hate time-sert or heli-coil. The time-sert is said to hold better. What I "hate", is when done with head on block, but most are since fast and cheap. Issues as many have seen me beat the drums on. Is metal fillings getting into cylinder, during the time-sert or heli-coil procedure with head on. If cylinder not already damage, and metal does indeed drop in. Which seems no matter how carefully procedure followed, it will 98 out of a 100 times.

Best is to remove head, which then the cost is considerable higher. But if you've a good lower end, is best to spend the extra $ now. How do you know if a good lower end (shot block). Well this is easy to detriment before blow out. With compression and oil pressure test. After spark plug blow out, compression can't be tested, until head repair. But reviewing service history from day/mile one is helpfully, at predicting what compression and oil pressure would be today. Also scoping cylinder, looking for damage or metal particles that may have already dropped in. Which I recommend a high-end scope for. As the $20 snake cameras scopes, aren't really going to give the best detail.

 

[Juanblzer]

It's possible the misfire is not caused by an ignition system problem, especially since the misfire returned on the same cylinder. A coolant leak into a cylinder can cause a misfire. When you pulled the old spark plug did the plug from number 8 look different than the others? Was it, for example, noticeably cleaner than the other seven?

electrode was gone and threads were melted. I posted an image in my original post in this thread.

 

[2001LC]

electrode was gone and threads were melted. I posted an image in my original post in this thread.

Which is typical of spark plug walking out, then blowing out of head.

 

[Bomar]

I had that happen about 9 years ago after using a cheap aftermarket coil pack.

I had a heli coil put in and have been running it since and put about 150k miles on it with no issues.

 

[Juanblzer]

I had that happen about 9 years ago after using a cheap aftermarket coil pack.

I had a heli coil put in and have been running it since and put about 150k miles on it with no issues.

i'm hoping this is the case... the old landcruiser toughness is my main hope... helicoil and send it

 

[Bomar]

I found an RV shop that did them all the time on RVs and Fords.

 

[Eyedaho]

The process of elimination using known good parts is always a solid troubleshooting process. Swap #8 plug with a different one to start, then the injector if that does not work.

If I suspected a failed injector of melting the plug, I would bench test the injector rather than risk further damage to a different cylinder.

 

[e9999]

I certainly would not get that engine running again before checking things seriously, and even then, not with any gas going to that cylinder.

 

[Juanblzer]

The process of elimination using known good parts is always a solid troubleshooting process. Swap #8 plug with a different one to start, then the injector if that does not work.

it's a bit more complicated than that... threads are suspect in the 8th cylinder spark plug hole... so I'm worried or reluctant or both to move forward.