GM Cavalier/Sunbird/Skyhawk/Firenza 1982-1994

Spark Plug Wires



See Figures 1 and 2

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Fig. Fig. 1: Checking plug wire resistance through the distributor cap with an ohmmeter

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Fig. Fig. 2: Checking individual plug wire resistance with a digital ohmmeter

At every tune-up/inspection, visually check the spark plug cables for burns cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil. Replace any damaged wiring.

Every 50,000 miles (80,000 Km) or 60 months, 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.

To check resistance, remove the distributor cap, leaving the wires in place. Connect one lead of an ohmmeter to an electrode within the cap; connect the other lead to the corresponding spark plug terminal (remove it from the spark plug for this test). Replace any wire which shows a resistance over 30,000 ohms. Generally speaking, it is preferable that resistance be below 25,000 ohms, but 30,000 ohms must be considered the outer limit of acceptability. It should be remembered that resistance is also a function of length; the longer the wire, the greater the resistance. Thus, if the wires on your car are longer than the factory originals, resistance will be higher, quite possible outside these limits.

Wire length can therefore be used to determine appropriate resistance values:

0-15 in. (0-38cm) - 3,000-10,000 ohms
15-25 in. (38-64cm) - 4,000-15,000 ohms
25-35 in. (64-89cm) - 6,000-20,000 ohms
Wire over 35 in. (89cm) - 25,000 ohms


If all of the wires must be disconnected from the spark plugs or from the distributor at the same time, be sure to tag the wires to assure proper reconnection.

When installing a new set of spark plug wires, replace the wires one at a time so there will be no mix-up. Start by replacing the longest cable first. Install the boot firmly over the spark plug. Route the wire exactly the same as the original. Insert the nipple firmly onto the tower on the distributor cap, then install the cap cover and latches to secure the wires. Be sure to apply silicone dielectric compound to the spark plug wire boots and tower connectors prior to installation.