1FZ-FE cylinder 3 burning up my plug

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I’m fairly new to my 80 series. I’ve done a ton of work on it and have run into a few issues that I can’t figure out. It’s a 1994. Shortly after picking it up I developed a top end knocking noise. Upon investigation I found that a couple spark plugs, that were in Reasonably good condition upon inspection, had stripped their holes. I installed Perma coils in the affected holes and obviously changed the rest of the plugs. Long story short, the cylinder 3 plug is having issues. The plug and Perma Plug threads that go on plug that protrude into the combustion chamber are experiencing extreme heat and burning up. At least that is what it appears to be. Wish I had pics to show the plug but believe me that there is not much that’s left that’s metal on the plug in cylinder 3. It’s happened at least 3 times now. It runs beautifully until it gets burnt up. No noise, no issues until it doesn’t provide spark anymore. Any thoughts on going forward. I plan a rebuild but am trying to figure out why this is happening and how to avoid it in the future. Thanks!
 
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NGK BKR5EGP are what went in this time. NGK BKR5EYA we’re in it last time.
I’m starting to think that the catalytic converter is plugged enough to cause excessive heat but still working enough to run good at an idle or low rpms. I just can’t quite wrap my head around that idea yet though. I’m a shade tree mechanic and my diagnostic skills are almost enough to get me in trouble sometimes. That’s why I’m asking the experts here. Thanks for any insight you have! It’s greatly appreciated! 😄
 
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The FSM specifies NGK BKR5EYA, or ND K16R-U.

The NGK "upgrade chart" that I'm seeing doesn't list the BKR5EGP at all, and doesn't show any platinum upgrade for the BKR5EYA. What led you to install the BKR5EGP?

I really doubt that a clogged catalytic converter would cause this. I would think you'd blow out every exhaust gasket before seeing it causing excessive cylinder temperatures. And why would it only affect one cylinder?

The first thing I would do, personally, is install NGK BKR5EYA spark plugs, then use a stethoscope to verify that each fuel injector is clicking similarly.
 
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The FSM specifies NGK BKR5EYA, or ND K16R-U.

The NGK "upgrade chart" that I'm seeing doesn't list the BKR5EGP at all, and doesn't show any platinum upgrade for the BKR5EYA. What led you to install the BKR5EGP?

I really doubt that a clogged catalytic converter would cause this. I would think you'd blow out every exhaust gasket before seeing it causing excessive cylinder temperatures. And why would it only affect one cylinder?

The first thing I would do, personally, is install NGK BKR5EYA spark plugs, then use a stethoscope to verify that each fuel injector is clicking similarly.
It’s the plug that autozone had for my vehicle. The reason it isn’t the plug is that it did the same thing with the correct ones. Thanks for the suggestion on the injectors. I’ll check them.
 
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There are 3 usual causes of disintegrated ground straps and insulation. They can definitely be related. 1. Pre-ignition or detonation 2. A bad plug seal/seat. This allows combustion gas to seep past the threads, the plug overheats and .... 3. A small head gasket leak. The ground strap and electrode insulator of the plug operate at 1000+ degrees . If they get nailed with coolant at that temp, they degrade very quickly.
 
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There are 3 usual causes of disintegrated ground straps and insulation. They can definitely be related. 1. Pre-ignition or detonation 2. A bad plug seal/seat. This allows combustion gas to seep past the threads, the plug overheats and .... 3. A small head gasket leak. The ground strap and electrode insulator of the plug operate at 1000+ degrees . If they get nailed with coolant at that temp, they degrade very quickly.
Upon investigation I am finding evidence that the combustion gas in leaking past the threads but it probably isn’t the plug seal. When this originally happened I had to install Perma Coils in 3 cylinders (the front 3). The plugs that were on from the previous owner were not old. After owning it for a couple thousand miles I began hearing some top end tapping. It was the plug wire cap tapping against the cover. One by one all 3 needed Perma Coils after changing the plugs. As for detonation, I get no sounds of that. If purs…until it burns out the plug. Unfortunately the locktite doesn’t work at those temps even it you follow ever step that they recommend. The Perma Coil threads usually come out (or partway out at least) with the plug. Unless it’s burnt up at the bottom. Then the threads get stuck and I have to use the tap to rime the leftovers. Looks like I may need a new head all things considered.
 
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Why did you have to permacoil the threads?!
As mentioned before I experienced plugs jumping out of the holes. If due to the previous owners mistake I can’t say. A tuneup was not at the top of the list that needed to be addressed. Cap and plug wires looked newer so I didn’t bother with them. Anyway the plugs stripped out of their holes in the 2000 miles I had it. Ended up having to put in the Perma Coils. Whatever caused those to strip Is causing my current problem too. Just trying to wrap my head around why.
 

SmokingRocks

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I'd bet the PO cranked down on the plugs when he put them in and damaged the threads probably multiple times. I doubt something else happened causing them to blow out. Unfortunately, if your spark plug threads are truly wrecked then it does seem like you'll need a new head.

Have you checked your timing? I wouldn't be surprised if the PO cranked it up over 12°, pinging/detonation more often than not impossible to hear or feel. Detonation would damage the plugs and eventually the threads.
 

SmokingRocks

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can you post a photo of the burnt plugs?

Also don't put in parts that show as compatible in autozones or oriellys database. These cars are oddly particular to OEM spec parts, make sure you put the sparkplugs recommend in your FSM / owners manual only, people having issues with other plugs is well documented here on mud
 
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I'd bet the PO cranked down on the plugs when he put them in and damaged the threads probably multiple times. I doubt something else happened causing them to blow out. Unfortunately, if your spark plug threads are truly wrecked then it does seem like you'll need a new head.

Have you checked your timing? I wouldn't be surprised if the PO cranked it up over 12°, pinging/detonation more often than not impossible to hear or feel. Detonation would damage the plugs and eventually the threads.
I’ve experienced detonation and it hasn’t really been sounding like there is pinging or detonation. I haven’t checked the timing. I gave my timing gun away years ago thinking that I’ll never have a vehicle again that will need it. Here I am.
 
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can you post a photo of the burnt plugs?

Also don't put in parts that show as compatible in autozones or oriellys database. These cars are oddly particular to OEM spec parts, make sure you put the sparkplugs recommend in your FSM / owners manual only, people having issues with other plugs is well documented here on mud
Thanks. I’ll be careful going forward for sure.
 
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Thanks. I’ll be careful going forward for sure.
Unfortunately I did not get a pic of the old one but here’s the newest one that was in #3. Perma Coil came out with it despite using red locktite and thread compound on the plug. I also swaged the coil as per instructions to allow the knurl at the top to bite. I let the locktite cure for 24 hours as well. You can kind of see where the exhaust was leaking past. Don’t know if it will come through but it is definitely a hot spot and something that the rest of the plugs don’t have.

image.jpg
 
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Thanks. I’ll be careful going forward for sure.
can you post a photo of the burnt plugs?

Also don't put in parts that show as compatible in autozones or oriellys database. These cars are oddly particular to OEM spec parts, make sure you put the sparkplugs recommend in your FSM / owners manual only, people having issues with other plugs is well documented here on mud
Unfortunately I did not get a pic of the old one but here’s the newest one that was in #3. Perma Coil came out with it despite using red locktite and thread compound on the plug. I also swaged the coil as per instructions to allow the knurl at the top to bite. I let the locktite cure for 24 hours as well. You can kind of see where the exhaust was leaking past. Don’t know if it will come through but it is definitely a hot spot and something that the rest of the plugs don’t have.

image.jpg
 

SmokingRocks

Don't tell my wife how much this actually cost...
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I'm wondering if you are not getting a good ground through the threads to the head. Also curious to know how much timing the motor has in it. Regardless it looks like you are in for a new head
 

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