GM Cadillac Deville_Fleetwood_ELD_Seville 1990-1998

Ignition Coil Pack


Each end of the secondary winding of an ignition coil is attached to a spark plug. Each cylinder is paired with the cylinder that is opposite it (1-4, 2-5, 6-7, 3-8). These cylinders are referred to as "companion" cylinders since they are on top dead center at the same time.

When the coil discharges, both plugs fire at the same time to complete the series circuit. The cylinder on the compression stroke is said to be the "event" cylinder and the one on the exhaust stroke is said to be the "waste" cylinder. The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug. The remaining energy will be used as required by the cylinder on the compression stroke. The same process is repeated when the cylinders reverse roles. This method of ignition is called a "waste spark" ignition system.

The Ignition coil design is improved, with saturation time and primary current flow increased. This redesign of the system allows higher secondary voltage to be available from the ignition coils-greater than 40kv. (40,000 volts) at any engine RPM. Secondary voltage requirements are very high with an open spark plug or spark plug wire. The ignition coil has enough reserve energy to fire the plug that is still connected, at idle, but the coil may not fire the spark plug under high engine load. A more noticeable misfire may be evident under load, both spark plugs may then be misfiring. Running for an extended period like this will burn out the coil.

This ignition control system has several advantages over a mechanical distributor ignition system:

  1. No moving parts to wear out
  3. No mechanical load on the engine
  5. Eliminate of mechanical timing adjustment
  7. Improved high engine speed performance

The Northstar ignition control system is composed of the following components:

Two crankshaft position sensors
Crankshaft reluctor ring
Camshaft position sensor
Ignition control module
4 separate ignition coils
8 spark plug wires and conduit
8 spark plugs
Knock sensor
Powertrain Control Module (PCM)

Four separate coils are mounted to the module assembly. Each coil provides the spark for 2 spark plugs simultaneously. Each coil can be replaced separately.


Before beginning the electrical testing of the coil pack, it is a good idea to perform some preliminary checks, these checks should also include a visual inspection of the circuits involved. These checks should include:

Check PCM grounds, make sure they are clean, tight, and in their proper location.
Check vacuum hoses for splits, kinks, and proper connections, as show on the Vehicle Emission Control Information label, and check thoroughly for any type of restriction.
Check the air intake ducts for collapsed or damaged areas.
Check air leaks at throttle body mounting area. Mass Air Flow (MAF) sensor and intake manifold sealing surfaces.
Check the ignition wires for cracking, hardness, proper routing, and carbon tracking.
Check the wiring for proper connection, pinches, and cuts. Check the insulation for evidence of rubbing against metal and weight through, causing a short to ground.


3.0L Engine
  1. Remove the wiper arms
  3. Remove the left and right side air inlet grilles
  5. Remove the wiper motor.
  7. Detach the power brake booster vacuum connection from the intake plenum.
  9. Disconnect the spark plug wiring harness from the ignition coil.
  11. Detach the electrical connection from the ignition coil.
  13. Remove the bolts from the ignition coil, and remove the coil.

To install:

  1. Installation is the reversal of the removal procedure.
  3. Tighten the coil bolts to 71 inch lbs. 8 (Nm).
  5. Tighten the power brake booster vacuum connection until snug.

4.6L Engines
  1. Remove the spark plug wires for corresponding ignition coils at the ignition control module assembly.
  3. Remove the ignition coil retaining bolts (2 per coil).
  5. Remove the coil from the IC module assembly.

To install:

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Fig. Unplug the coil assembly connectors for the control and . . .

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Fig. . . . for the trailing side

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Fig. Remove the coil pack retaining bolts

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Fig. It is easier to unbolt the entire assembly before removing the individual spark plug wires. Make sure they are tagged beforedisassembly

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Fig. Remove the screws that hold the coil in place

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Fig. Lift up the individual coil that needs to be replaced and remove it from the rest of the coil pack

  1. Install the ignition coil to the IC module assembly with the 2 retaining bolts, tighten to 30 inch lbs. (3.5 Nm).
  3. Install the spark plug wires at the IC module assembly.