226k miles on Copper Plugs

[BryanTDI12]

Back in February I did a bunch of catch-up maintenance on my Uncle's 2005 Toyota Tacoma with the 4.0V6 engine in it. He has only replaced oil+filter and the cabin filter on the truck. Here's what the original copper plugs look like; original gap is 0.043in. I know they are original because of the 2 different brands that Toyota put at the factory (NGK and Denso). The truck never misfired but it was getting about 12mpg on the freeway. Replacement schedule is every 30k miles, but seeing that they went 7.5times their life, why replace them at 30k?

For anyone interested, I replaced/changed
-Mobil 1 HM 5w30 and Toyota Filter
-Toyota Pink Coolant
-Cabin FIlter
-Engine Air Filter (probably original too, had a huge amount of fine dust and the pre-screen was loaded with dirt)
-Valvoline Synpower 75w90
-Trans Drain&Fill with ATF WS (original fluid didn't look too bad)
-Power Steering D&F with Valvoline Dexron VI
-DOT3 brake fluid - full brake bleed
-3 U-joints

 

[CarbonSteel]

Gaps that wide had to be stressing the coil(s). I would not replace them at 30K, but I would not go 226K either. Every 100K or so would be preferable, I should think.

 

[hattaresguy]

Just goes to show that the modern iridium plugs are pretty much life time.

Copper plugs going that distance is pretty impressive.

 

[NMBurb02]

The Densos look like they held up better than the NGKs. What were the gaps on the old ones?

 

[Nukeman7]

"... I know they are original because of the 2 different brands that Toyota put at the factory (NGK and Denso). "

Why would Toyota use two different plugs manufacturers on the production line for this engine assembly? Doesn't seem to align with Toyota's quality control philosophy and lean build practices at all (google Kaizen and Training Within Industry). It would appear to me that this resulted from someone (perhaps a garage) who replaced some or all of the original plugs during a previous tune-up.

 

[4wheeldog]

Originally Posted By: Nukeman7
"... I know they are original because of the 2 different brands that Toyota put at the factory (NGK and Denso). "

Why would Toyota use two different plugs manufacturers on the production line for this engine assembly? Doesn't seem to align with Toyota's quality control philosophy and lean build practices at all (google Kaizen and Training Within Industry). It would appear to me that this resulted from someone (perhaps a garage) who replaced some or all of the original plugs during a previous tune-up.



My '96 Tacoma and my '00 4runner (Both with 3.4 V6) had the same odd thing going on, with the OEM plugs. Those were waste spark motors, and the info I was given was that Toyota put them in that way, because one brand wore better with the backwards spark.

Why they would do it with the 4.0, which is an individual coil pack motor.......The only reason that comes to mind is they have 2 suppliers for plugs, and the plugs are installed in the heads before they go on they go on the block. My '05 V6 Tacoma did NOT have 2 brands of plugs, from the factory. All were NGK.

 

[HerrStig]

Toyota ignition systems get a thumbs up from me. That kind of wear and gap might be hard on a plug wire set, though.

 

[cptbarkey]

Did he deliberately neglect them as some sort of experiment or was it an honest mistake? I personally would not treat an engine that way knowingly.

Could be manufacturing quality differences, or that cylinder head was worked harder on that side of the engine for any number of reasons.

 

[BryanTDI12]

Originally Posted By: Nukeman7

Why would Toyota use two different plugs manufacturers on the production line for this engine assembly? Doesn't seem to align with Toyota's quality control philosophy and lean build practices at all (google Kaizen and Training Within Industry). It would appear to me that this resulted from someone (perhaps a garage) who replaced some or all of the original plugs during a previous tune-up.



I don't know why Toyota would do that but it was NGK on the right bank and Denso on the left. Google "NGK Denso Tacoma" and there's a bunch of threads with the same kind of thing happening. My uncle has never taken it to a shop, and I asked if had changed anything but he's only done oil changes and cabin filter (after the fact that the HVAC air blower broke because of all the dirt/junk from driving on dirt roads and parking under trees)

 

[BryanTDI12]

Originally Posted By: cptbarkey
Did he deliberately neglect them as some sort of experiment or was it an honest mistake? I personally would not treat an engine that way knowingly.



He drives them till they die, and didn't know that things other than oil needed replacing. The owners manual in the glovebox has been collecting dust.

The same with his 1995 Chevy K1500, only oil changes.