Ignition Coil and Iridium Spark Plugs for GMC Envoy (2002-2005) 4.2L

Direct-Replacement Ignition Kit for 2002-2005 GMC Envoy

What it Does: Complete 6-cylinder ignition tune-up kit engineered to restore factory secondary spark voltage, stabilize idle quality, and eliminate engine misfires under load.

The Stock Envoy Ignition Degradation

The factory coil-on-plug packs on the GMT360 platform endure severe thermal cycling directly atop the deep spark plug wells of the 4.2L inline-six cylinder head. Over extended mileage, the original internal epoxy insulation deteriorates, leading to dielectric breakdown, intermittent spark flashover, and cylinder-specific misfire codes (P0300–P0306). Worn factory plugs experience ground electrode erosion, creating an excessively wide gap that overworks aged coils and causes stumbling under acceleration, rough idle, and decreased fuel efficiency.

The Engineering Solution

This direct-fit overhaul kit upgrades your ignition system with heavy-duty internal copper windings encased in reinforced, high-dielectric housings to withstand thermal saturation. Premium silicone boots seal tightly over the plug well to prevent moisture contamination and voltage leakage. Paired with fine-wire iridium spark plugs, the assembly produces a concentrated, high-intensity spark kernel for rapid flame propagation, restoring dependable cold-weather starting, crisper throttle response, and complete combustion across all cylinders.

Technical Specifications

Compatibility

• 2002 GMC Envoy (SLE, SLT) 4.2L L6
• 2003 GMC Envoy (SLE, SLT) 4.2L L6
• 2004 GMC Envoy (SLE, SLT) 4.2L L6
• 2005 GMC Envoy (SLE, SLT) 4.2L L6
• 2002-2005 GMC Envoy XL / XUV 4.2L L6

The GMC Utility Standard

Engineered to meet the rigorous demands of daily hauling, trailering, and stop-and-go commuting, this ignition setup ensures consistent cylinder pressure and uncompromised low-end torque retention across the lifetime of your drivetrain.