In the 1990s, many auto manufacturers switched from the distributor cap to the coil pack, also known as an ignition coil pack. These packs work by using a copper coil in conjunction with the car’s computer to apply high voltage, often in excess of 35,000 volts, to the spark plug wires of the vehicle. This process ignites any fuel in the chamber of the engine and provides power to move the vehicle. These units solve a number of reliability problems with traditional distributor caps and provide a number of benefits. While these parts are generally dependable for at least 100,000 miles, failure can occur. When this happens, replacement is often required to alleviate the problem.

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Benefits of Using a Coil Pack

  • Increased Efficiency: These packs are able to apply higher voltages than traditional distributor caps in many cases. This allows for more complete combustion of fuels. The overall results are fewer residues within the engine, increased horsepower and possible improvements in fuel economy. Further boosts can be seen using dual pack modules for high performance vehicles.
  • Improved Durability: Traditional distributor caps are prone to water damage and contain moving parts. This pack uses magnetism and computer management to achieve better results with fewer moving parts. This allows some of these packs to last 150,000 miles or more before needing replacement. They will also operate without fault even if submerged in water.

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This pack will eventually fail due to aging. When this occurs, coil pack testing and replacement is often a simple and affordable process. With basic tools and a few hours, most novice mechanics can replace a coil pack themselves for additional coil pack cost savings. Due to the amount of copper contained in the coil pack, many parts distributors will often provide a small discount on a new pack if you trade in your failed pack as well.

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Common Coil Pack Symptoms

  • Hesitation and jerking during heavy acceleration such as climbing hills or accelerating to highway speeds
  • Rough Idle
  • Intermittent exhaust
  • Frequent blinking of the fuel warning light when the fuel tank is full
  • Intermittent blinking of check engine light
  • Significant loss of engine power

Fortunately, coil pack testing is simple. Common tools needed include a multi-meter and the specified mega-ohm information about your pack. Specifications can vary greatly depending on the make and model of your vehicle. If you are unable to find information in your owner’s manual or on the Internet, consulting a local mechanic or factory garage will often provide the information you need.

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Once you have this information, testing is as simple as checking the performance of the coil pack using your multi-meter. In most cases, checking at the coil itself is recommended. When checking through the spark plug wire, ensure the wires are in proper condition to eliminate their failure as a cause. If the power provided from the pack is not within specified tolerances, it should be replaced immediately. Replacement pack units are available at most auto parts retailers as well as on the Internet or through your factory garage.