Nissan 240SX/Altima 1993-1998 Repair Guide

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

Spark plug wires should be inspected at every tune-up/safety inspection. Visually check the spark plug wires for burns, cuts or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil pack. Replace any damaged wiring.

Every 60,000 miles (96,600 km), 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 isolate the cause of high resistance, first check the resistance of the spark plug wire on the distributor cap. Then remove the spark plug wire from the distributor cap and check it separately.

To check resistance, remove the distributor cap from the distributor and disconnect the spark plug wires from spark plugs. Using a digital ohmmeter, measure the resistance between the terminal inside the distributor cap and the terminal at the spark plug end of the wire. Resistance should be resistance should be between 4.15-5.61 kilohms per foot. Move each wire while testing to check for intermittent breaks. If resistance is not within specification on one or more wires, replace the entire set of wires.


See Figures 3 and 4

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Fig. Fig. 3: Always label the spark plug wires prior to removal

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Fig. Fig. 4: Remove the spark plug wires one at a time and make a note of their routing

  1. Label each spark plug wire and make a note of its routing.

Don't rely on wiring diagrams or sketches for spark plug wire routing. Improper arrangement of spark plug wires will induce voltage between wires, causing misfiring and surging. Be careful to arrange spark plug wires properly.

  1. Starting with the longest wire, disconnect the spark plug wire from the spark plug and then from the distributor.

To install:
  1. If replacing the spark plug wires, match the old wire with an appropriately sized wire in the new set.
  3. Lubricate the boots and terminals with dielectric grease and install the wire on the distributor. Make sure the wire snaps into place.
  5. Route the wire in the exact path as the original and connect the wire to the spark plug.
  7. Repeat the process for each remaining wire, working from the longest wire to the shortest.