3RZFE engine Spark Plugs & Coil Wires (question about which specs are important)

I found this NGK spark plug decoder ring.
The differences appear to be only in the material used for the center electrode (I think).
They say it's a 30,000 mile plug but the previous plugs went at least double that (I think).

 

On your original plugs, they are definitely worn. Not a bad thing at all, the wore well. The third plug had a little bit of oxidation around the threads but whoopty doo. Maybe the plug boot wasn't all the way down. Regardless, doesn't matter, they're burning well.
Oh sweet on the part numbers, yeah that makes sense. As you're seeing, the material the electrode is made of is how the manufacturers pick a good for xx amount of miles. 30k mile is fine, only thing the more expensive plug will do is last longer between needing to be changed.
Your compression numbers look great too. Nice healthy engine.
The next 'maintenance' step would be the valves and checking them and and likely swap out some shims as they've of course worn. I also have the 3RZ and at this age and mileage we're getting to where the valves will wear down to low and then not open and close for their full duration which will cause us to burn a valve. This spring/summer I am gonna be pulling the valve cover to check valve lash and shim accordingly. Looks like this could be your next step as well. There are write ups and I think videos as well on doing this. And the FSM of course is always good to have on hand, and while valve cover is off might as well replace the gasket. And since the throttle body is off might as well clean it out and make sure the IAC is all clear.... sounds like only an evening of wrenching

 

Thanks for that spark plug analysis. The plugs are in order, from 1 to 4 with the number 1 cylinder (that had the misfire) at the top.

I'll be more diligent moving forward as those plugs must easily have had more than twice that mileage.

I really don't want to rip the engine apart but you're right I should check the valves and timing chain as neither has ever been checked in 200K miles over more than two decades of daily use.

I have this old motorocycle valve bucket depressor tool. Do you think it would work?
And is checking the timing chain at the same time of checking valves a lot more work?

 

That tool may work. One of the valve threads on here had a guy who had done it a couple times and tried a few of the different tools and came back with the one or two that were most effective for him. And if I memba right it was the two most basic tools lol Like a pic thing and then a pry tool or something like that. I'll see if I can find that thread or something similar.
And no need to jump right on it if you're not having any problems and with those compression numbers I wouldn't think you're burning or close to burning a valve. Even with the age and miles. I've been around Toyota for a long time. But certainly jump straight in as your heart desires, just didn't want you to think it was imperative that the valve train be inspected asap only on the age or mileage. And the timing chain is also very robust and the guides and tensioner are very reliable as well.
Inspecting the timing chain would be a good thing to do while doing the valves.
Are there any specific symptoms or possible symptoms that are pushing you to inspect these sooner rather than later? Or solely just wanting to stay on top of the maintenance?

 

Thanks. The whole thing with "specialty tools" is you only generally use them once, so, while they pay for themselves in that one use, it's best if they can be used at least twice!

Thanks. Since I've never done either on a car I don't know if it's one of those jobs that has us remove the same parts. If so, it makes sense to check both the timing chain and valve clearance at the same time. But I'd rather NOT rip open a perfectly good engine either, if I don't have to (as I've never done it before).

There are no symptoms whatsoever other than this sudden P0301 which turned out to be bad plugs or wires since that cleared it up instantly.
I'm just worried that I might damage something if I overlook the chain and/or valves because I know they've never been checked in 200K miles.

BTW, one "special tool" that I used "twice" was these hose clamp pliers, which I used to pull out the tip of the broken spark plug wire that was stuck on the spark plug preventing me from getting the 5/8ths inch spark plug socket on any of the plugs.

 

Yeah man nice work. It definitely pays to be resourceful and open minded when it comes to doing your own work.
Since you don't have anything you have to address asap symptom wise, I'd say that'll allow you some time to read up or watch some vids on it. Also maybe even have the shims on hand when you start measuring the valve lash. The valve lash can be checked rather easily with just removing the things to get to valve Cover and then removing that. You'll be able to measure the valves rather easily compared to making adjustments on which shims you need for meeting valve lash spec. Just an option. Nice to have options and to be able to plan it out instead of the valves telling you they need addressing RIGHT NOW lol

 

I ran a set of densos on a 01 3rz for almost 250k. They still worked and I think I have them in a drawer actually