How To Replace Spark Plugs
Written by isaac
Photos by DSGB4LYF23
Toyota recommends the following Iridium spark plugs...
Iridium plug, 14mm, 5/8" hex, gap 1.1mm (0.043")1ZZ-FE (2000+ Celica GT)
DENSO - SK16R11
NGK - IFR5-T112ZZ-GE (2000+ Celica GTS)
DENSO - SK20R11
NGK - IFR6-T11As per the 2000+ Toyota Celica Owner's Manual:
Use only iridium-tipped spark plugs and do not adjust the gaps for you engine performance and smooth drive-ability.
...Iridium Spark Plug Info:
Iridium is a precious metal that is 6 times harder and 8 times stronger than platinum, it has a 1,200F higher melting point than platinum and conducts electricity better. This makes it possible to create the finest wire center electrode ever.
Prior till now, spark plug manufacturers have favored platinum for their long life or performance spark plugs due to its high melting point, also the technology did not exist to machine and bond iridium on a spark plug electrode(at least in a cost effective manner). Champion spark plugs had already made an iridium industrial application spark plug, but it still sells for over a hundred dollars per plug.
Just now is the technology available to effectively use iridium in a spark plug for automotive applications. The strength, hardness and high melting point of iridium make it very well suited for a fine wire plug.
The primary iridium plug manufacturers at this time are Denso with a 0.4mm center electrode and NGK with a 0.7mm center electrode. Both are the best performance plugs on the market for traditional automotive use and many racing applications.
SIDE NOTE: Thus far the tech's we have spoken with report no problems using iridium plugs with Nitrous.
Iridium Technical PDF...http://www.sparkplugs.com/pdfs/iri.pdfTRD Iridium 'Racing Spark Plugs' Part # 19059-sp004-22 plug type IK22TRD
Racing plugs are Denso IK22 are the same as the standard Denso Iridium Power (0.4mm Tip) Plug, one heat-range colder than what is specified by Toyota (IK20/SK20R11). You can buy them without the TRD
branding for about $12/each - probably less.
The recommended GTS spark plugs are one heat-range colder than the recommended GT spark plugs.
Colder heat-range plugs help stop pre-ignition, and are generally used in highly tuned normally aspirated and forced induction engines. For an example close to home, the 1ZZ plug heat-range is 16, whereas the 2ZZ heat-range is 20, 1 heat-range colder.
For a standard internals road car there is probably not much advantage to go for a colder plug, unless you drive you car in the 7-8000RPM range for extended periods.
Though, for the Celica GTS, it is recommend to use a these colder plugs because of its VVTL-I tech. A downside of cold plugs is that they foul easier than hot plugs.How to change:
[*] 10mm Socket
[*] 16mm (5/8") Hex Spark Plug Socket
[*] Socket Wrench
[*] Socket Extender
The next two photos are of how to remove the Celica 1ZZ-FE (2000+ Celica GT) "Cosmetic" Cylinder Head Cover (plastic engine cover)...
NOTES: The 2ZZ-FE (2000+ Celica GTS) "Cosmetic" Cylinder Head Cover (plastic engine cover) has a slightly different look, but is removed basically the same way as shown above.
Once the cosmetic Cylinder Head Cover has been removed, the spark plug coils are visible and regardless of the 7th Gen Celica engine model, the replacement procedures are basically the same.
Using the 10mm socket wrench, disconnect the 4 ignition connectors.
Now remove the 2 bolts from the wire harness protector.
Pull out the 4 ignition coils (with igniter).
Using a 16mm (5/8") Hex Spark Plug Socket Wrench, remove the spark plugs.INSTALLATION IS IN THE reverse ORDER OF REMOVAL
Torque: 18 N-m (184 kgf-cm, 13 ft-lbf)