Scope and preparation
Use this with the linked illustrated procedure and VIN-specific repair instructions for an original N20/N26 F30 328i. Confirm the replacement plugs and coils before dismantling anything. Work on a cooled engine, with ignition off and the key away. Photograph the cowl and harness routing. Have the correct thin-wall plug socket, hand tools, a suitable torque wrench and any required replacement access fasteners ready.
Access and remove
The documented job removes the engine cover, relevant cowl pieces and brace for access. Release coil connectors using their locks rather than pulling wires. Lift the coils out and inspect the wells before opening a cylinder. Debris or pooled fluid needs attention before plug removal. Keep removed parts indexed by cylinder so unusual deposits can be discussed with a technician.
Seat plugs without forcing threads
Start each correct plug by hand with a suitable installation tool. If it binds early, stop rather than using the ratchet to force it. NGK specifies dry installation for its plated plugs and warns that anti-seize changes tightening behavior. Protect fine-wire electrodes. Use the plug/application specification, not a universal BMW torque from a forum.
Reconnect and verify
Seat the coils fully and lock the electrical connectors. Reassemble the access components using the complete repair procedure; do not omit the angle stage or replacement requirements for brace hardware. Check for trapped harnesses and leftover fasteners. Start the engine and verify normal operation before road use. If a misfire begins immediately afterward, stop and recheck the work instead of assuming every new component is good.
Sources / references 2
- FCP Euro: N20/N26 ignition service ↗Reviewed Oct 6, 2026
- NGK: five spark-plug installation facts ↗Reviewed Oct 6, 2026
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