What Are my Spark Plugs Trying to Tell me?

[RPC]

Had a few extra bucks to work on my truck so I replaced the spark plugs today.

What I pulled out were darker around the business end of the threaded body and “ashier” around the ground electrode than I expected. ~101k mi. on the originals, 90% highway and 99% 87 octane.

What are these trying to tell me?

*replaced original plugs (all 8 of which were identical) with NGK Iridium Lasers

 

[2016 4Runner SR5]

They're telling you nothing. They appear to be in very good condition actually.

 

[AuSeeker]

I agree those plgs look just fine and normal, the threaded portion doesn't matter, what your seeing there is carbon which is normal, the only portions that matter is the insulator, electrode and the ground electrode, all of which looks normal.

Here are several different photo charts with descriptions for you and others to look at.

http://www.globaldenso.com/en/products/aftermarket/plug/basic_knowledge/troubleshooting/index.html

NGK Spark Plugs

Verrill: Plug Color Chart

https://www.vulcandrifterriders.com/sparkplugcolorchart.html

 

[Atlanta_man]

Same thing mine told me at 100K miles: "we are good for 200K, put us back"

 

[RPC]

Thanks all for the input.

The reason driving this change in plugs was a code my BlueDriver code reader keeps identifying: P1378 Preignition Detected. Been hard to to find much info on this code, but a few callouts I have found circle back to spark plugs potentially being the culprit.

Code Reader:

 

[AuSeeker]

It's strange that it's coming up in "Body Codes" and "Back Door Codes"!!

The only thing I could find for that code was "fuel injection control module curcuit low voltage"

I did see where a guy had that code with preignition detected on a 2006 Toyota Avalon and Scotty Kilmer suggested changing the plugs and if that didn't help to clean the fuel injectors, because they could have debris in them and causing them to leak thus causing the preignition.

Otherwise I couldn't find other referrences to that code, seems to be a somewaht obscure code.