Ignition Coil and Iridium Spark Plugs for Lincoln Navigator (2018-2021) 3.5L

Direct-Fit Ignition Coil and Iridium Spark Plug Tune-Up Kit for 2018-2021 Lincoln Navigator (U554)

What it Does: The ignition coil and iridium spark plug kit replaces aged factory ignition components on the 2018-2021 Lincoln Navigator to eliminate high-boost misfires, stabilize idle quality, and restore peak combustion efficiency.

The Stock Lincoln Navigator Secondary Ignition Breakdown

Under heavy throttle and high manifold boost pressures, the high-output Gen 2 3.5L EcoBoost D35 engine demands excessive secondary ignition voltage to bridge plug gaps. Over time, thermal cycling degrades the factory coil-on-plug epoxy insulation and weakens the internal windings, leading to internal voltage arcing and spark blow-out. Worn standard or degraded electrodes widen the spark gap, forcing the factory coil pack past its dielectric breakdown threshold. This results in intermittent cylinder misfires, unburnt fuel washing down cylinder walls, rough idling, diagnostic trouble codes (P0300-P0306), and sluggish throttle response while towing or accelerating under load.

The Engineering Solution

This refresh kit pairs high-dielectric coil-on-plug units with fine-wire iridium spark plugs specifically engineered to resist spark quench in forced-induction environments. The ignition coils utilize vacuum-impregnated, heat-resistant epoxy-filled housings to insulate internal windings against heat-induced voltage leakage, paired with durable fluorosilicone boots and a factory-matching 3-blade harness terminal. The complementary iridium spark plugs feature a laser-welded fine-wire center electrode, substantially lowering the necessary ignition voltage while resisting electrode erosion and maintaining a consistent gap across extreme thermal cycles. This ensures immediate spark propagation and complete flame front distribution in every combustion chamber.

What's Included

• 6 Black Direct-Fit Ignition Coils
• 6 Fine-Wire Iridium Spark Plugs

Technical Specifications

Compatibility

• 2018 Lincoln Navigator 3.5L V6 Twin Turbo (Base, Select, Reserve, Black Label, L)
• 2019 Lincoln Navigator 3.5L V6 Twin Turbo (Base, Select, Reserve, Black Label, L)
• 2020 Lincoln Navigator 3.5L V6 Twin Turbo (Base, Reserve, Black Label, L)
• 2021 Lincoln Navigator 3.5L V6 Twin Turbo (Standard, Reserve, Black Label, L)

Frequently Asked Questions & Fitment Warnings

Does this fit the U554 Navigator?

Yes, this is a direct fit for the fourth-generation 2018-2021 Lincoln Navigator equipped with the Gen 2 3.5L EcoBoost engine. This kit does not fit 2015-2017 first-generation 3.5L EcoBoost engines due to different coil dwell and mounting geometry.

Should dielectric grease be used during installation?

Applying a thin film of dielectric grease inside the spark plug boot tips prevents moisture intrusion, stops high-voltage flashover, and facilitates future boot removal from the ceramic insulators.

The Lincoln Towing and Durability Standard

Engineered to handle sustained loads and heavy towing, this ignition refresh guarantees reliable spark delivery under the elevated cylinder pressures and thermal demands inherent to twin-turbocharged platforms.