Nissan Murano Ignition Coil Replacement

The Nissan Murano, known for its stylish design and comfortable ride, relies on a dependable ignition system to deliver optimal performance. At the heart of this system are the ignition coils, responsible for providing the high-voltage spark needed to ignite the air-fuel mixture in each cylinder. When these coils falter, the consequences can range from a slight decrease in fuel efficiency to a complete engine misfire. This article provides a comprehensive guide to replacing the ignition coils on a Nissan Murano, covering everything from diagnosis to the replacement procedure.

Understanding Ignition Coils and Their Function

Before diving into the replacement process, it's crucial to understand the role of ignition coils. An ignition coil is essentially a transformer that steps up the low voltage from the car's battery (typically 12 volts) to the high voltage (ranging from 20,000 to 40,000 volts) needed to create a spark at the spark plug. This spark ignites the air-fuel mixture in the combustion chamber, initiating the power stroke that drives the engine. Modern Muranos typically use a coil-on-plug (COP) system, meaning each spark plug has its dedicated ignition coil. This design enhances efficiency and reduces potential points of failure compared to older distributor-based systems.

Symptoms of Failing Ignition Coils

Identifying a failing ignition coil early can prevent more significant engine damage. Common symptoms include:

Engine Misfires: This is the most prevalent symptom. A misfire occurs when one or more cylinders fail to fire properly, resulting in a rough idle, hesitation during acceleration, and a noticeable decrease in power. You might also feel a shaking or vibrating sensation, especially at lower speeds.
Check Engine Light (CEL): A failing ignition coil will often trigger the CEL. The OBD-II (On-Board Diagnostics II) system will store a diagnostic trouble code (DTC) indicating the specific cylinder experiencing the misfire (e.g., P0301 for cylinder 1, P0302 for cylinder 2, etc.).
Poor Fuel Economy: When a cylinder misfires, unburnt fuel is expelled into the exhaust system, leading to a decrease in fuel efficiency. You might notice that you're filling up your gas tank more frequently than usual.
Rough Idling: A failing ignition coil can cause the engine to idle roughly, resulting in noticeable vibrations and an unstable RPM reading on the tachometer.
Difficulty Starting: In some cases, a severely failing ignition coil can make it difficult to start the engine, especially in cold weather.

Tools and Materials Required

Before starting the ignition coil replacement, gather the necessary tools and materials:

New Ignition Coils: Purchase replacement ignition coils specifically designed for your Nissan Murano's year and engine type. Using the correct parts is crucial for proper performance. Consult your owner's manual or a reliable auto parts store to identify the correct part number. Brands like Denso, NGK, and Delphi are known for their quality and reliability.
Socket Set: A socket set with various sizes is essential for removing the engine cover and securing the ignition coils. A 10mm socket is commonly used.
Wrench Set: A wrench set might be needed for accessing certain components.
Screwdrivers: Both flathead and Phillips head screwdrivers may be required.
Torque Wrench: A torque wrench is crucial for tightening the ignition coil bolts to the manufacturer's specified torque, preventing damage to the coil and ensuring proper contact.
Multimeter (Optional): A multimeter can be used to test the resistance of the old ignition coils to confirm a failure.
Dielectric Grease: Applying dielectric grease to the spark plug boot of the new ignition coil helps prevent corrosion and ensures a good electrical connection.
Pen and Paper (or Digital Device): To record the location of each coil as you remove it, especially if you suspect only one or two are failing.
Work Gloves: To protect your hands.
Safety Glasses: To protect your eyes.

Step-by-Step Ignition Coil Replacement Guide

Important Safety Precautions: Disconnect the negative battery cable before starting any work on the electrical system. This prevents accidental electrical shocks and protects the vehicle's electronic components. Ensure the engine is cool to avoid burns.

Locate the Ignition Coils: On a Nissan Murano, the ignition coils are typically located on top of the engine, directly above the spark plugs. They are usually covered by an engine cover that needs to be removed.
Remove the Engine Cover: Use a socket or wrench to remove the bolts securing the engine cover. Carefully lift the cover off the engine.
Disconnect the Electrical Connector: Each ignition coil has an electrical connector attached to it. Gently press the release tab on the connector and pull it straight off the coil. Avoid pulling on the wires.
Remove the Ignition Coil: Use a socket to remove the bolt securing the ignition coil to the engine. Once the bolt is removed, gently pull the ignition coil straight up and out of the spark plug well. Note the location of each coil, especially if only replacing one or two.
Inspect the Spark Plug Well: Before installing the new ignition coil, inspect the spark plug well for any debris, oil, or coolant. Clean the well if necessary.
Apply Dielectric Grease: Apply a small amount of dielectric grease to the inside of the spark plug boot on the new ignition coil. This helps prevent corrosion and ensures a good electrical connection.
Install the New Ignition Coil: Carefully insert the new ignition coil into the spark plug well, ensuring it is fully seated.
Secure the Ignition Coil: Tighten the ignition coil bolt to the manufacturer's specified torque using a torque wrench. Over-tightening can damage the coil, while under-tightening can cause it to loosen over time. Refer to your vehicle's repair manual for the correct torque specification.
Reconnect the Electrical Connector: Plug the electrical connector back onto the ignition coil until it clicks into place. Ensure the connector is securely attached.
Repeat for Remaining Coils: Repeat steps 3-9 for any remaining ignition coils that need to be replaced.
Reinstall the Engine Cover: Reinstall the engine cover and secure it with the bolts you removed earlier.
Reconnect the Negative Battery Cable: Reconnect the negative battery cable to the battery.
Start the Engine: Start the engine and listen for any unusual noises or vibrations. If the engine runs smoothly and the CEL is off, the ignition coil replacement was successful.
Clear Diagnostic Trouble Codes (Optional): If the CEL was illuminated before the replacement, you may need to clear the DTCs using an OBD-II scanner. Even if the light goes off on its own, clearing the codes ensures the system is properly reset.

Testing Ignition Coils (Optional)

If you are unsure which ignition coil is failing, you can use a multimeter to test the resistance of each coil. Here's how:

Set the Multimeter: Set the multimeter to the resistance setting (Ohms).
Disconnect the Ignition Coil: Disconnect the electrical connector from the ignition coil.
Test the Primary Resistance: Place the multimeter probes on the two terminals of the ignition coil's primary winding (the terminals where the electrical connector attaches). Note the resistance reading.
Test the Secondary Resistance: Place one multimeter probe on the spark plug terminal of the ignition coil and the other probe on one of the primary winding terminals. Note the resistance reading.
Compare Readings: Compare the resistance readings of each ignition coil. A significantly different reading compared to the others may indicate a faulty coil. Consult your vehicle's repair manual for the specific resistance values for your Murano's ignition coils.

Important Note: Testing ignition coils with a multimeter only provides an indication of their condition. A coil can still fail under load even if it passes a resistance test. If you suspect an ignition coil is failing, replacing it is often the best course of action.

Troubleshooting Common Issues

Even with careful execution, issues can sometimes arise after replacing ignition coils. Here are a few common problems and how to address them:

Engine Still Misfires: If the engine continues to misfire after replacing the ignition coils, consider the following:
- Spark Plugs: The spark plugs may be worn or damaged. Inspect and replace them if necessary.
- Fuel Injectors: A clogged or malfunctioning fuel injector can cause a misfire.
- Vacuum Leaks: Vacuum leaks can disrupt the air-fuel mixture, leading to misfires.
- Compression Issues: Low compression in one or more cylinders can also cause misfires. A compression test can help diagnose this issue.
Check Engine Light Remains On: If the CEL remains on after replacing the ignition coils, use an OBD-II scanner to read the DTCs. Ensure the new ignition coils are properly connected and functioning correctly.
Rough Idling Persists: If the engine continues to idle roughly, check for vacuum leaks, faulty sensors (such as the mass airflow sensor), or issues with the engine's idle control system.

Preventative Maintenance

To prolong the life of your ignition coils and prevent future issues, consider the following preventative maintenance measures:

Regular Spark Plug Replacement: Worn spark plugs can put extra strain on the ignition coils. Replace the spark plugs according to the manufacturer's recommended interval.
Proper Engine Maintenance: Regular oil changes and other maintenance tasks help keep the engine running smoothly, reducing stress on the ignition system.
Avoid Excessive Idling: Excessive idling can cause the engine to overheat, which can damage the ignition coils.
Use Quality Fuel: Using high-quality fuel helps prevent deposits from forming on the spark plugs and fuel injectors, which can improve engine performance and reduce stress on the ignition system.

Conclusion

Replacing the ignition coils on a Nissan Murano is a relatively straightforward task that can be accomplished with basic tools and mechanical knowledge. By following the steps outlined in this guide, you can restore your Murano's performance and fuel efficiency. Remember to prioritize safety and consult your vehicle's repair manual for specific instructions and torque specifications. Regular maintenance and prompt attention to any symptoms of ignition coil failure will help ensure your Murano runs smoothly for years to come. Always use OEM or high-quality aftermarket parts to guarantee compatibility and durability. With proper care, your Nissan Murano will continue to provide a comfortable and reliable driving experience.