BMW G80 M3 Spark Plugs & Coils (S58)
Fresh ignition transforms how a twin-turbo S58 runs — crisper response, no misfires under boost. It's a satisfying DIY across all six cylinders, with one twist for the enthusiast: a tuned car wants a colder plug and earlier intervals. Here's how to do plugs and coils properly.
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On a forced-induction engine, tired plugs and coils show up as misfires and stumble under boost long before a regular car would notice. The S58 has six cylinders, each with its own coil-on-plug, and the job is straightforward once you've cleared the plumbing on top to reach them. Do plugs and coils as a set, and if the car's tuned, fit the right colder plug.
Parts & Tools You'll Need
Six plugs, six coils, and the right gap for your setup.
Step-by-Step
Cool Engine, Battery Off
Work on a cold engine to avoid damaging the alloy threads, and disconnect the battery (or at least switch off the ignition) before handling the coils.
Clear the Plumbing on Top
Remove the engine cover and any charge-pipe or intake plumbing in the way to reach the coil pack area. Note how it comes off so reassembly is straightforward.
Unplug & Pull the Coils
Release each coil connector, free the retaining clip and pull the coil-on-plug straight up. Work one cylinder at a time so nothing gets mixed up or dropped.
Remove the Old Plugs
With the plug socket and extension, unscrew each plug. Blow or wipe away any debris around the plug wells first so nothing falls into the cylinder.
Gap & Fit the New Plugs
Check each new plug's gap against spec (tighter for a tuned, high-boost car), add a trace of anti-seize, thread by hand to avoid cross-threading, then torque to spec — never guess.
Fit New Coils & Reassemble
Press the new coils onto the plugs, reconnect each connector and clip, then refit the plumbing and cover in reverse. Reconnect the battery.
Start & Verify
Start the engine — it should idle smoothly with no misfire and no warning light. A quick scan confirms there are no stored ignition faults. Take a short drive to confirm clean boost.
Cold engine, correct gap, correct torque
Only fit plugs into a cold engine — hot alloy threads strip easily. Verify the gap on every plug (a tuned, high-boost S58 typically wants a colder plug and a tighter gap) and torque to spec rather than overtightening. Get these three right and the job is foolproof; rush them and you risk a stripped plug well or misfires under boost.
Quick Specs
General guidance — verify for your exact car and setup.
| Item | Detail |
|---|---|
| Plugs | Six; OE heat range stock, one step colder if tuned |
| Gap | To spec; tighter on a high-boost tuned car |
| Coils | Six coil-on-plug; replace as a set with plugs |
| Interval | ~40–60k mi; sooner (e.g. ~half) if tuned/tracked |
| Access | Remove charge-pipe/intake plumbing on top |
FAQ
How often should I change the S58's plugs?
Roughly every 40,000–60,000 miles on a stock car, but sooner if it's tuned or tracked — many tuned owners halve the interval, because higher boost is harder on plugs. Coils are replaced with them as a set.
Do I need colder plugs?
On a tuned, higher-boost S58, yes — a one-step-colder plug helps control knock and is cheap insurance with a tune. On a stock car the standard heat range is correct. Follow your tuner's recommendation for plug and gap. See the tuning guide.
Should I replace the coils too?
Yes — do plugs and coils together. They wear as a set, you've already done the labor to reach them, and fresh coils prevent the misfires that tired ones cause under boost.
What gap should I run?
The factory gap on a stock car; a tighter gap on a tuned, high-boost setup to maintain a strong spark. Always verify the gap on every plug before fitting and follow your tuner's spec if modified.
Why work on a cold engine?
The cylinder head is aluminum, and hot alloy threads strip far more easily. Let the engine cool fully before removing or installing plugs, and torque them to spec rather than overtightening.
You're Done
Fresh plugs and coils across all six cylinders — crisper response and clean boost with no misfires. The rules: cold engine, the right plug and gap (colder and tighter if tuned), coils with plugs, and torque to spec. Pair it with the oil change and, if you're adding power, the S58 tuning guide. Back to the G80 hub.