2008 Nissan Altima Coil Pack

The 2008 Nissan Altima, like many modern vehicles, utilizes a coil-on-plug (COP) ignition system. This system, a significant advancement over older distributor-based ignitions, places individual ignition coils directly above each spark plug. This guide delves into the intricacies of the 2008 Altima's coil pack system, examining its components, function, diagnostics, and potential issues.

Understanding the Coil-on-Plug (COP) System

Before diving into the specifics of the Altima, let's understand the advantages of a COP system. The key benefit is the elimination of the distributor. Distributors, while reliable in their time, introduced limitations due to mechanical complexity and the finite time available to distribute spark to each cylinder, especially at higher RPMs. COP systems, controlled electronically by the engine control unit (ECU), offer:

Improved Spark Timing Accuracy: The ECU directly controls each coil, allowing for more precise and dynamic spark timing adjustments, crucial for optimal engine performance and fuel efficiency.
Increased Spark Energy: By minimizing energy loss through long high-voltage wires (as in distributor systems), more energy reaches the spark plug, leading to more complete combustion.
Enhanced Reliability: Eliminating the mechanical distributor reduces the number of moving parts, potentially increasing system reliability. However, individual coil failures are still possible.
Simplified Diagnostics: Individual coil control allows for cylinder-specific fault diagnosis through OBD-II codes.

Components of the 2008 Altima Coil Pack System

The 2008 Altima's COP system consists primarily of the following:

Ignition Coils: These are the heart of the system, each responsible for generating the high-voltage spark needed to ignite the air-fuel mixture in a single cylinder. They are typically mounted directly on top of the spark plugs.
Spark Plugs: These provide the gap across which the high-voltage spark jumps, igniting the air-fuel mixture. Proper spark plug gap and condition are crucial for optimal coil performance.
Engine Control Unit (ECU): The ECU is the brain of the engine management system. It receives information from various sensors and uses this data to determine the optimal spark timing and duration for each cylinder. It then sends signals to the individual ignition coils.
Crankshaft Position Sensor (CKP): This sensor monitors the crankshaft's position and speed, providing essential timing information to the ECU.
Camshaft Position Sensor (CMP): The CMP sensor, in conjunction with the CKP sensor, helps the ECU determine the precise position of each cylinder in the firing order. This is particularly important for sequential fuel injection and ignition.
Wiring Harness: The wiring harness connects all the components of the ignition system, providing power and control signals to the coils.

The Ignition Coil: A Closer Look

The ignition coil is a type of transformer that steps up the battery's 12-volt supply to the tens of thousands of volts needed to create a spark. It consists of two main windings:

Primary Winding: A coil of thick wire with relatively few turns. When the ECU grounds the primary circuit, current flows through this winding, creating a magnetic field.
Secondary Winding: A coil of thin wire with many thousands of turns. This winding is connected to the spark plug.

When the ECU interrupts the current flow through the primary winding, the magnetic field collapses rapidly. This collapsing magnetic field induces a very high voltage in the secondary winding, which is then discharged across the spark plug gap, creating the spark.

How the System Works

The 2008 Altima's ignition system operates in a precise sequence:

The CKP and CMP sensors provide the ECU with information about crankshaft and camshaft position, allowing the ECU to determine which cylinder is ready to fire.
Based on engine load, RPM, and other factors, the ECU calculates the optimal spark timing.
The ECU grounds the primary circuit of the corresponding ignition coil. Current flows through the primary winding, building a magnetic field.
At the precise moment determined by the ECU, the ground connection to the primary winding is interrupted.
The magnetic field collapses rapidly, inducing a high-voltage pulse in the secondary winding.
This high-voltage pulse is discharged across the spark plug gap, igniting the air-fuel mixture.
The process repeats for each cylinder in the engine's firing order.

Common Problems and Diagnostics

While COP systems are generally reliable, problems can occur. The most common issue is a faulty ignition coil. Symptoms of a bad coil pack can include:

Misfires: The most obvious symptom. A misfire occurs when a cylinder fails to fire properly, resulting in rough running, reduced power, and poor fuel economy.
Check Engine Light (CEL): A misfire will often trigger the CEL. OBD-II codes will typically indicate which cylinder is misfiring (e.g., P0301 for cylinder 1 misfire).
Rough Idling: The engine may idle roughly or stall.
Poor Fuel Economy: Incomplete combustion due to misfires leads to reduced fuel efficiency.
Hesitation or Stuttering During Acceleration: The engine may hesitate or stutter when accelerating.
Loss of Power: A noticeable decrease in engine power.

Diagnostic Procedures

Diagnosing a faulty coil pack typically involves the following steps:

Read OBD-II Codes: Use an OBD-II scanner to retrieve diagnostic trouble codes (DTCs). Pay attention to misfire codes (P0300-P0304, P030x where x is the cylinder number).
Visual Inspection: Inspect the ignition coils for any signs of physical damage, such as cracks, burns, or corrosion. Check the wiring harness and connectors for loose connections or damaged wires.
Coil Swapping: This is a common and effective diagnostic technique. Swap the suspected faulty coil with a known good coil from another cylinder. Clear the DTCs and drive the vehicle. If the misfire code follows the swapped coil, the coil is likely faulty. For example, if P0301 (cylinder 1 misfire) is present, swap coil 1 with coil 2. If the code changes to P0302 (cylinder 2 misfire), then the original coil 1 is likely bad.
Resistance Testing: Use a multimeter to measure the resistance of the primary and secondary windings of the coil. Compare the readings to the manufacturer's specifications (refer to the 2008 Altima service manual). Significant deviations from the specified resistance indicate a faulty coil. Caution: Disconnect the coil from the wiring harness before performing resistance testing.
Spark Testing: Use a spark tester to verify that the coil is producing a strong spark. Caution: This test involves high voltage. Follow the manufacturer's instructions and take necessary safety precautions.
Check Spark Plugs: Inspect the spark plugs for wear, damage, or fouling. Replace the spark plugs if necessary, ensuring they are properly gapped to the manufacturer's specifications. A worn or improperly gapped spark plug can put extra strain on the coil and lead to premature failure.
Wiring Harness Inspection: Carefully inspect the wiring harness and connectors leading to the ignition coils. Look for any signs of damage, corrosion, or loose connections. Use a multimeter to check for continuity and voltage at the coil connector.

Maintenance and Replacement

While ignition coils are generally maintenance-free, there are steps you can take to prolong their lifespan:

Replace Spark Plugs Regularly: As mentioned earlier, worn spark plugs can put extra strain on the coils. Follow the manufacturer's recommended maintenance schedule for spark plug replacement.
Keep the Engine Clean: A clean engine bay helps prevent overheating, which can damage the coils.
Address Misfires Promptly: Ignoring a misfire can lead to further damage to the ignition system and catalytic converter.

Replacing an ignition coil on the 2008 Altima is a relatively straightforward process:

Disconnect the negative battery terminal.
Locate the faulty ignition coil (identified through diagnostic procedures).
Disconnect the electrical connector from the coil.
Remove the mounting bolt or bolts securing the coil to the engine.
Carefully remove the coil from the spark plug well.
Install the new coil, ensuring it is properly seated on the spark plug.
Secure the coil with the mounting bolt or bolts.
Reconnect the electrical connector.
Reconnect the negative battery terminal.
Clear any DTCs and test drive the vehicle to ensure the misfire is resolved.

Important Considerations: Always use quality replacement parts from reputable manufacturers. Consider replacing all ignition coils at the same time, especially if one coil has failed due to age or wear. This can help ensure consistent performance and prevent future failures. Refer to the 2008 Nissan Altima service manual for specific torque specifications and procedures.

Conclusion

The 2008 Nissan Altima's coil-on-plug ignition system represents a significant improvement over older ignition designs, offering enhanced performance, efficiency, and reliability. Understanding the components, function, and diagnostic procedures associated with this system allows for effective troubleshooting and maintenance, ensuring optimal engine performance and longevity. By following the guidelines outlined in this guide, owners and enthusiasts can confidently diagnose and address common issues related to the Altima's coil pack system.