GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Spark Plug Wires


Your vehicle is equipped with an electronic ignition system which utilizes 8mm wires to conduct the hotter spark produced (except 2.3L engine). The boots on these wires are designed to cover the spark plug cavities on the cylinder head. The 2.3L and 2.4L engines do not use spark plug wires. The coil assembly is connected directly to the spark plug with rubber connectors.


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: 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 each plug wire and test one at a time. Connect one lead of an ohmmeter to the electrode within the wire on the cap end; connect the other lead to the corresponding spark plug terminal end of the wire. Replace any wire which shows a resistance of over 30,000 ohms. Always coat the terminals of any wire that is removed or replaced with a thin layer of dielectric compound.


When installing a new set of spark plug cables, replace the cables 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; if so equipped, be sure to route the wire through the corrugated tubing. Make sure the wire is clamped in all its retainers, and that the terminals inside the boots snap into place. Repeat the process for each cable.