CHECKING AND REPLACEMENT
At every tune-up, visually inspect the spark plug cables for burns, cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and coil. Replace any damaged wiring. Every 36,000 miles (58,000 km) or so, the resistance of the wires should be checked with an ohmmeter. Wires with excessive resistance will cause misfiring and may make the engine difficult to start in damp weather. Generally, the useful life of the cables is 36,000-50,000 miles (58,000-80,000 km).
It should be remembered that resistance is also a function of length; the longer the cable, the greater the resistance. Thus, if the cables on your car are longer than the factory originals, resistance will be higher, quite possibly outside these limits.
When installing new cables, always replace them one at a time to avoid mix-ups. Start by replacing the longest one first. Install the boot firmly over the spark plug. Route the wire over the same path as the original. Insert the nipple firmly into the tower on the cap or the coil.
To check resistance, perform the following:
- Remove the distributor cap, leaving the wires attached. To remove and check the ignition wires on the 3S-GTE engine, the intercooler must be removed (see .)
- Tag and remove the spark plug wires one at a time from the spark plugs. Take care not to damage them by bending them or pulling on the wires themselves.
- Connect one lead of an ohmmeter to an electrode within the cap; connect the other lead to the corresponding spark plug wire end. Replace any wire that shows a resistance over 25,000 ohms.
- If the resistance is out of specification, replace the ignition wire and/or the distributor cap.