GM Bonneville/Eighty Eight/LeSabre 1986-1999

Spark Plug Wires

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TESTING



See Figure 1

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 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 wires from the coil and spark plug. 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. The following chart gives resistance values as a function of length. Generally speaking, however, resistance should not be considered the outer limit of acceptability.

  1. 0-15 in. (0-38cm): 3,000-10,000 ohms.
  2.  
  3. 15-25 in. (38-64cm): 4,000-15,000 ohms.
  4.  
  5. 25-35 in. (64-89cm): 6,000-20,000 ohms.
  6.  
  7. Over 35 in. (89cm): 25,000 ohms.
  8.  



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Fig. Fig. 1: Checking individual plug wire resistance with a digital ohmmeter

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 possibly outside these limits.

REMOVAL & INSTALLATION



See Figures 2, 3 and 4

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

  1. Disconnect the negative battery cable, and if the vehicle has been run recently, allow the engine to thoroughly cool.
  2.  
  3. If equipped, remove the retainer, then lift the engine cover off for access to the spark plug wires.
  4.  

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.

  1. Carefully twist the spark plug wire boot 1 / 2 turn in each direction to loosen it, then pull upward and remove the boot from the plug. Be sure to pull on the boot and not on the wire, otherwise the connector located inside the boot may become separated. Repeat the process to disconnect the wire from the ignition coil.
  2.  



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Fig. Fig. 2: Pull the spark plug wire off the plug by the boot, NOT the wire



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Fig. Fig. 3: Spark plug wire routing - 3.8L (VIN C) engine shown



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Fig. Fig. 4: During installation, make sure the spark plug wires are properly routed - 3.8L (VIN 1 and K) engine shown

To install:

On these engines, aluminum heat shields are used over the spark plug boots on cylinders located near the exhaust tubing. Make sure the heat shield are fully seated during installation.

  1. Install the boot firmly over the spark plug and push until it clicks into place. The click may be felt or heard, then gently pull back on the boot to assure proper contact. Route the wire exactly the same as the original, through all convolute tubing and clamped in all holders. Insert the nipple firmly onto the tower on the ignition coil. Be sure to apply silicone dielectric compound to the spark plug wire boots and tower connectors prior to installation.
  2.  
  3. Repeat the process for each cable, making sure ends snap into place.
  4.  
  5. If necessary, position the engine cover, then secure it in place using the retainer.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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