2019 Isuzu NPR Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2019 Isuzu NPR is crucial for optimal engine performance, fuel efficiency, and longevity. The spark plug's primary job is to ignite the air-fuel mixture in the combustion chamber, and doing so effectively requires the right heat range and electrode material.

Heat Range: This refers to the plug's ability to dissipate heat. A plug that's too "cold" (dissipates too much heat) can lead to fouling, while one that's too "hot" (dissipates too little heat) can cause pre-ignition or detonation, leading to engine damage. The OEM-specified heat range is engineered for the specific operating conditions of your NPR's 6.0L engine.

Electrode Metal:

• Iridium: These are standard for your 2019 Isuzu NPR 6.0L engine. Iridium is extremely hard and has a very high melting point, allowing for very fine electrodes. This results in a more concentrated spark, better ignitability, and significantly extended service intervals (typically 100,000 miles or more).
• Platinum: While not typically found in the 2019 Isuzu NPR from the factory, platinum plugs offer a step up from copper in terms of durability and lifespan. They use a platinum disc welded to the center electrode and/or ground electrode to resist wear, offering service life around 60,000-80,000 miles.
• Copper: These are the traditional spark plugs. Copper is an excellent conductor of electricity, but it's a softer metal, so copper plugs have larger electrodes and a shorter lifespan (around 30,000 miles). They are not suitable for your 2019 Isuzu NPR.

How to gap a spark plug

Although most iridium spark plugs come pre-gapped from the factory, it's always a good practice to double-check the gap before installation, especially after handling. An incorrect gap can lead to misfires or poor combustion. For your 2019 Isuzu NPR 6.0L, the specified gap is 0.040 inches (1.0 mm).

To gap a spark plug, you'll need a wire-type spark plug gapping tool. Avoid using disc-style gapping tools on fine-wire iridium plugs, as they can damage the delicate electrode.

1. Measure the gap: Carefully slide the correct wire gauge from your tool between the center and ground electrodes. It should slide in with a slight drag.
2. Adjust (if necessary): If the gap is too small, use the gapping tool's electrode BENDER to gently pry up the ground electrode. If the gap is too wide, gently tap the ground electrode on a clean, hard surface to close the gap. Make very small adjustments and remeasure frequently.
3. DO NOT bend the center electrode.

Replacement procedure tips

Replacing the spark plugs on your 2019 Isuzu NPR with the 6.0L engine is a straightforward process, but a few tips can make it smoother:

• Coil-on-plug (COP) Removal: Your 6.0L engine uses a coil-on-plug ignition system. Each spark plug has its own individual ignition coil mounted directly on top of it. To access the spark plugs, you'll need to disconnect the electrical connector from each coil and then remove the coil mounting bolt. Gently twist and pull the coil straight up to remove it from the spark plug well. Be careful not to damage the coil boot.
• Anti-seize Debate: There's ongoing debate about using anti-seize compound on spark plug threads. For plugs with nickel-plated shells, like the OEM ACDelco and most aftermarket iridium plugs, manufacturers typically advise against anti-seize. The plating acts as a release agent. Applying anti-seize can alter the torque readings, leading to over-tightening and potential damage to the cylinder head threads. Follow the spark plug manufacturer's recommendations. If you choose to use it, use a very small amount and reduce the torque specification by approximately 10-15%.
• Dielectric Grease on Boots: A small dab of dielectric grease inside the spark plug boot (the part that connects to the top of the spark plug) can be beneficial. It helps seal out moisture, prevents corrosion, and makes future removal easier.
• One at a time: Replace one spark plug at a time to avoid mixing up ignition coil wiring, although with a COP system this is less of a concern.
• Torque Wrench: Always use a torque wrench to tighten spark plugs to the specified 11 lb-ft (15 Nm). Over-tightening can strip cylinder head threads or crack the spark plug porcelain, while under-tightening can lead to combustion gas leakage and overheating.

Known issues

The 6.0L engine in your 2019 Isuzu NPR is generally reliable and does not have specific widespread spark plug-related issues like the Ford 3-valve 2-piece design. However, common issues that can lead to spark plug symptoms include:

• Ignition Coil Failure: While the spark plugs themselves are durable, individual ignition coils (COPs) can fail, leading to misfires. If you experience a misfire after spark plug replacement, consider testing or replacing the coil for that cylinder.
• Carbon Buildup: Excessive carbon buildup in the combustion chamber can foul spark plugs prematurely, especially if the engine is experiencing other issues that lead to incomplete combustion.

Need plugs replaced? Find a shop on Repairius.