Spark plug wires

Wires and caps do not wear like mechanical parts, but do age with time and usage. The outer sheath on older types are made of a synthetic rubber like EPDM. The thick insulation prevents arcing from the cable to an earthed engine component. A rubber "boot" covers each terminal. Dielectric grease can be used to improve insulation; a small amount can be applied in the inside of the rubber boot at each end of each wire to help seal out moisture. When your Toyota is also used during rain, this grease forms a neccessary improvement (https://www.crcindustries.com/products/dielectric-grease-3-3-wt-oz.html).

Inspecting and testing the sparkplug wires :

First of all check the wires and cap on corrosion, cracks, burns and cuts.  Any burn marks on the wire indicates on a crack in the sheath, which can lead to misfiring. The inner core of a spark plug wire was traditional made of copper or aluminium. Even withoun these signs of deterioration a wire can be faulty. To check you need a Ohm meter. It should read between 5000 and 8500 ohm. Is it much higher, the innercore is probably damaged and the wire needs replacement. Lower resistant is always better and most new wires nowadays are measuring 1000 Ohm or less.

Newer spark plug wires (and most replacements) nowadays have a very flexible and heat-resistant silicone rubber outer sheath and the core is a;uminium or nickel. Higher quality ones, like the ones we sell from Top-performance use carbon as core material which also reduce the spread of electromagnetic fields (interference). Resistance is 1000 Ohm or lower.