Replacing Spark Plugs

[Eric]

Since I was replacing a few other engine components I decided it was time to replace twelve spark plugs. My 1997 has ~135,000 km and I don't know the last time they were changed. I have a strong feeling they were changed once before. Usually Toyota factory plugs have an ink dot at the very top of the spark plug.

The Century has a recommended replacement every 100k km for spark plugs. They're not as easy to access as many other Toyota engines. You need to remove a lot of intake components: both throttle bodies, each intake air connector, both intake air surges.

Disclaimer: I need to lookup the official cylinder numbers for the 1GZ-FE engine. But for this post I'm assuming driver side = odd number, passenger side = even cylinder number.

Here is my 12 old ones. Notice the highly scientific spark plug holder.
Arrow indicates engine front. Notice on passenger side, cylinder tube 4 had oil, good reason to change spark plug tube gaskets at the same time.

[Eric]

Here is driver side spark plugs. Cylinders 1-3-5-7-9-11. Cylinder 7-9-11 were worse than front half. A little corona staining on the back three as well.



Passenger side Cylinders 2-4-6-8-10-12. Similar pattern of wear. Cylinder 12 was the worst.

[Eric]

A closer inspection, just for fun.

Cylinder 1:



Cylinder 12:

[Eric]

Torque each plug to 8.5 Nm
(6.27 ft lbs or 75 inch pounds [rounded])

Here is the diagram, spark plugs are in middle of picture.



After installing sparks plug reinstall each ignition coil and wire. The 1997-2010 has plug and wire. Starting in 2010 it fully transitioned to x12 coil on plug.

Here is driver side for reference:



Passenger side:
I took the picture before I reconnected the wiring.