How to Test Subaru Spark Wires Like a Pro: Step-by-Step Guide for Optimum Performance

If you are a Subaru car owner or auto mechanic, you may have experienced performance issues at some point. One of the common causes of such problems is a faulty spark wire. Understanding how spark wires function and how to test them is essential to troubleshoot performance issues effectively. In this article, we will discuss how to test Subaru spark wires like a pro using a multimeter, common signs that indicate faulty spark wires, and troubleshooting tips to diagnose common issues.

What Are Spark Wires and How Do They Function?

Spark wires are essential components of the ignition system of a car. They are responsible for delivering high voltage electricity from the ignition coil to the spark plug, which ignites the fuel-air mixture in the combustion chamber. This ignition process results in the movement of pistons, which powers the car’s engine.

When the spark wires are working correctly, the voltage delivered from the ignition coil to the spark plug is consistent, resulting in optimal fuel combustion and engine performance. However, if the spark wires are faulty, they can cause a misfire, resulting in reduced power, rough idling, and poor fuel economy.

Common Signs That Indicate Faulty Spark Wires

There are various signs that indicate faulty spark wires. Some of the most common ones include:

  • Misfiring engine: A misfiring engine occurs when one or more cylinders fail to ignite, causing the car to shake or vibrate.
  • Rough idling: If the engine idles roughly, it may be due to the spark plugs not firing correctly, causing the engine to run inconsistently.
  • Poor acceleration: If the car is not accelerating correctly, it may be due to a spark plug not firing correctly, causing the engine to work harder than necessary.
  • Reduced power: A fault in the spark wires can cause a decrease in engine power, making it difficult to drive uphill or maintain high speeds.
  • Poor fuel economy: When the spark wires fail, it can cause the engine to work harder than necessary, resulting in poor fuel economy.
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Step-by-Step Guide to Testing Subaru Spark Wires

Testing the spark wires in your Subaru is a simple process that can be done using a multimeter. The following are the steps to test spark wires:

Step 1: Turn off the engine.

Step 2: Locate the spark wires.

You can find the spark wires under the hood of your Subaru. They are usually connected to the ignition coil and the spark plugs. You may need to remove a plastic cover to access them.

Step 3: Remove the spark wires.

Carefully remove the spark wires from the ignition coil and the spark plugs. Make sure you label them or note their positions to avoid mixing them up later.

Step 4: Attach the multimeter.

Set your multimeter to the ohms setting and connect the positive and negative leads to the corresponding terminals on the spark wire. The resistance should be between 2 kΩ and 20 kΩ, depending on the vehicle model.

Step 5: Test each spark wire.

Test each spark wire by connecting the multimeter to the corresponding terminals. If the resistance reading is outside the normal range, it indicates a faulty spark wire that needs to be replaced.

Step 6: Replace the faulty spark wires.

If any of the spark wires have resistance readings outside the normal range, it is essential to replace them with new ones. You can purchase genuine Subaru spark wires from authorized dealerships or online stores.

Troubleshooting Tips for Diagnosing Common Issues

If you have tested the spark wires and found them to be working correctly, but you are still experiencing performance issues, the following troubleshooting tips can help you diagnose the problem:

  • Check the spark plugs: Faulty spark plugs can also cause performance issues and may need to be replaced.
  • Inspect the ignition coil: If the ignition coil is faulty, it can cause weak or no spark, resulting in engine misfires.
  • Check the fuel system: If the fuel system is clogged or not functioning correctly, it can cause reduced power and poor fuel economy.
  • Check the air filter: A dirty air filter can restrict the airflow, causing a decrease in engine performance.
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Q: How often should Subaru spark wires be tested?

A: Spark wires should be tested as part of a regular maintenance routine, which is usually every 30,000 miles or as recommended in the owner’s manual.

Q: Can I test spark wires without a multimeter?

A: While testing spark wires with a multimeter is the most accurate method, you can also do a visual inspection of the wires for signs of damage or wear.

Q: How much do Subaru spark wires cost?

A: The cost of Subaru spark wires varies depending on the vehicle model and the dealership or online store you purchase them from. On average, they range between $60 and $120.


Testing Subaru spark wires is a simple process that can help you diagnose and troubleshoot performance issues effectively. By understanding what spark wires are and how they function, identifying common signs of failure, and following the step-by-step instructions for testing them with a multimeter, you can ensure optimal performance of your Subaru. Remember to replace any faulty spark wires to avoid further damage to your vehicle.

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Davis Bellew

As a Subaru owner and enthusiast, Davis has a deep understanding of the needs and concerns of Subaru drivers. He specializes in writing informative and engaging content about Subaru maintenance and repair, and his articles are always well-researched and easy to understand. When he's not writing, he enjoys hiking and photography.

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