GM Century/Lumina/Grand Prix/Intrigue 1997-2000

Spark Plug Wires


Use care not to damage the spark plug wires (more properly called the secondary ignition wires) or the spark plug boots. Rotate each boot about one half turn to dislodge it from the plug or coil tower before removing it from either the spark plug or the ignition coil. Never pierce a secondary ignition wire or boot for any testing purposes. Future problems are guaranteed if pinpoints or test lights are pushed through the insulation for testing.

The spark plug wiring used with these ignition systems is a carbon impregnated cord conductor encased in a 7mm or 8mm diameter silicone rubber jacket. The silicone jacket is designed to withstand very high temperatures. The silicone spark plug boots form a tight seal on the plug. The boot should be twisted one-half turn before removing. Care should also be used when connecting a timing light or other pick-up equipment. Do not force anything between the boot and wiring, or through the silicone jacket. Connections should be made in parallel using an adapter. Do not pull on the wire to remove. Pull on the boot, or use a tool designed to remove spark plug boots.


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Fig. 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, disconnect the spark plug end and coil end of one spark plug wire. Connect an ohmmeter to lead to each end of the spark plug wire's terminals. A general rule is to replace the wire if the resistance is over 30,000 ohms. It should be remembered that resistance is a function of wire length and a longer wire may have more resistance. Today's vehicles are factory equipped with top quality spark plug wires since they must carry enormous amounts of energy, and, if treated carefully, generally give little trouble for the life of the vehicle.


If all of the wires must be disconnected from the spark plug s or the ignition coil pack 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. Twist the boot of the spark plug wire 1 / 2 turn in each direction before pulling it off. 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 ignition coil. Transfer any boot heat shields, plug wire conduits and retaining clips to the new wires. On some V6 engines, the front engine mount strut must be removed and the engine rotated, or pulled forward in its mounts to access the rear spark plug wires. For details regarding rotating the engine, please refer to the procedure located earlier in this section.

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Fig. On vehicles equipped with heat shields, make sure they are seated against the bump stop and the lower tabs extend over the plug's hex

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Fig. Spark plug wiring layout-2000 3.4L (VIN E) engine shown, 2000 3.1L (VIN M) engine similar

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Fig. Spark plug wiring layout-2000 3.8L (VIN K) engine shown