The 2013 MINI Cooper S that limped into the shop last March presented a textbook intermittent fault. The owner, a graphic designer who daily-drives the car in Portland, described a rough idle and a flashing check-engine light that appeared only during heavy rain. By the time the car reached the bay, the symptoms were gone. Classic.
The codes told a partial story: P0301 and P0302 — misfires on cylinders one and two. No coolant loss, no vacuum leaks on the smoke test, compression was within spec. The spark plugs were replaced six months prior with correct NGK units. The ignition coil, however, was the original factory unit with 74,000 miles on it. The giveaway was a fine hairline crack on the coil housing, barely visible without a bright light and a careful hand. On a damp morning, that crack let moisture track straight down to the spark plug well, shorting the voltage to ground. Dry weather? The coil worked fine. Rain? Misfire city.
The fix was straightforward, but the choice of replacement part mattered. MINI’s R56-generation Cooper S uses a pencil-style coil that sits deep in the valve cover — a design that’s sensitive to both heat and vibration. We replaced all four coils rather than just the cracked one, because once one factory coil fails, the others are close behind. The customer opted for the OSRAM OS1067, a direct replacement for the OE part number 12138678438. Fitment was identical to the factory unit — same length, same connector angle, same locking tab. No adapters, no wiring modifications. The whole job took about an hour.
| Spec | OS1067 |
|---|---|
| Brand | OSRAM |
| Type | Pencil / Coil-on-plug |
| OE Reference | 12138678438 |
| Primary Resistance | 0.5 Ω ±10% |
| Secondary Resistance | 8.5 kΩ ±15% |
| Warranty | 12 months |
What impressed me wasn’t just the bolt-on fit — it was the dwell time behavior. I logged the OSRAM coil’s charge time against the factory spec on my oscilloscope. The current draw curve matched the OEM profile almost exactly. That’s important on the N18 engine, which uses a smart charging strategy through the engine computer. A coil that draws too much current or charges too slowly can trigger false misfire codes even when the part is new. We saw zero correlation issues after install. Cold starts at 38°F were smooth, and the rain test — a deliberate drive-through from a car wash with the hood release pulled — produced no hesitation.
The owner’s report two months later: no recurrence of the flashing light, smoother idle at stoplights, and a noticeable improvement in part-throttle response below 2,500 RPM. The old coil’s degradation was likely robbing spark energy even when it wasn’t fully shorting out. For a car with 74,000 miles, the ignition system refresh was overdue.
Common mistake I see from DIY owners and even some shops: replacing only the spark plugs when a P0301 code appears on an R56. The plugs are cheap and easy, so it’s the lazy path. But if the plugs are under 10,000 miles old and the coil is original, test the coil’s secondary resistance first. A reading outside the 7–10 kΩ range means replacement. Also, check the rubber boot inside the coil for cracks — that’s where moisture gets in.
For anyone with a 2011–2015 MINI Cooper S or Clubman S experiencing damp-weather misfires, start with the coils, not the plugs. The OS1067 from Longwei Parts is currently our go-to recommendation for this engine. It’s priced well below the dealer part, carries a one-year warranty, and in our experience, has a lower early-failure rate than some of the budget no-name coils we’ve tested. If your car is past 60,000 miles and still on factory ignition components, treat the coils as a service item — they’re not built to last forever.
Recommended Part: OS1067 – OE-grade replacement, in stock now.
