Symptoms
Misfire codes (P0300-series), rough idle, hesitation under boost. Often the plugs' age is simply unknown.
The fix, step by step
- Remove the engine covers and intake trim, pull each coil, and replace all eight plugs with Mercedes-spec plugs torqued to the service manual figure.
- Euro Premium Parts' M157 guide recommends inspecting or replacing the coils at the same time, at about 40,000–50,000 miles.
- Before replacing a coil, check its connector and boot for oil.
Tools & part numbers
- Thin-wall spark plug socket
- extensions and swivel
- torque wrench
- dielectric grease
Where to buy the parts
Genuine Mercedes spark plug kit 004 159 81 03 (×8, listed 2013–18 G63)FCP Euro ↗Amazon ↗
Bosch ignition coil kit 276 906 05 01 (×8, listed 2013–18 G63)FCP Euro ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz G 63 AMG parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.