Ignition Coil + Iridium Spark Plugs for Mercedes Benz GL-Class (2013-2016) 4.7L 5.5L

Direct-Fit Ignition Coil and Double Iridium Spark Plug Kit for 2013-2016 Mercedes Benz GL-Class 4.7L, 5.5L (X166 / M278, M157)

What it Does: The ignition coil and double iridium spark plug kit replaces aged factory ignition components on the 2013-2016 GL-Class to eliminate high-load misfires, restore lost combustion efficiency, and stabilize idle quality.

The Stock Mercedes Benz GL-Class Ignition Breakdown

The twin-turbocharged M278 and M157 engines in the X166 chassis generate immense cylinder pressures and thermal loads within an enclosed engine bay. Over time, the factory coil packs suffer dielectric breakdown in the internal epoxy and secondary windings due to prolonged heat soak. Concurrently, factory spark plug gaps widen under boost, elevating the required firing voltage and overworking the coil drivers. This leads to common high-load spark blowout, rough idle, stored DTCs (such as P0300 through P0308), and intermittent limp-mode activation under wide-open throttle.

The Engineering Solution

This service kit pairs direct-fit coil-on-plug modules with Bosch ZR6SII3320 double iridium spark plugs to withstand high-boost combustion environments. The coils feature reinforced thermoplastic housings and high-temperature silicone boots that isolate secondary voltage and resist micro-arcing against the cylinder head. Matched with fine-wire iridium center electrodes and platinum-ground pads, this setup maintains precise gap dimensions, lowers ignition voltage demand, and delivers consistent multi-strike spark energy across the entire rev range.

Technical Specifications

Compatibility

• 2013-2014 Mercedes Benz GL-Class GL450 4.7L V8 Biturbo (M278)
• 2013-2016 Mercedes Benz GL-Class GL550 4.7L V8 Biturbo (M278)
• 2013-2016 Mercedes Benz GL-Class GL63 AMG 5.5L V8 Biturbo (M157)

Frequently Asked Questions

Does this fit the X166 GL-Class?
Yes, this is a direct fit for the 2013-2016 Mercedes Benz GL-Class equipped with the M278 4.7L or M157 5.5L bi-turbo V8 engines.

What torque spec should be used when installing these spark plugs?
Torque the Bosch spark plugs to 23 Nm (17 lb-ft) into a cold aluminum cylinder head without anti-seize to ensure proper indexing and heat dissipation.

The Mercedes Benz Precision Standard

Direct-injected biturbo European platforms require exact secondary ignition tolerances to prevent catalyst damage and false knock detection. This complete overhaul kit guarantees seamless ECU integration without check engine lights or adaptation resets.