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2018 Mini Cooper S Misfire on Cylinder 2 - Rough Idle & CEL

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David L. · rep 0 · May 22, 6:51 AM · 1 replies · solved · Question

Vehicle: 2018 Mini Cooper S

Hey everyone,

I'm having an issue with my 2018 Mini Cooper S, F56 chassis. A few days ago, the car started running really rough, especially at idle, and the Check Engine Light came on. It was flashing at first, then went solid.

I hooked up my OBD-II scanner and pulled a P0302 code, which indicates a misfire on cylinder 2. The car feels sluggish and vibrates quite a bit when stopped. It's got about 65,000 miles on it.

What are the most common culprits for a P0302 on these Minis? I'm hoping it's something relatively simple I can tackle myself before taking it to a shop. Any advice on where to start looking would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:51 AM

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ClearTheCode admin answer:

A P0302 code on your 2018 Mini Cooper S (F56) indicates a misfire specifically on cylinder 2. This is a common diagnostic code that can stem from several issues related to the ignition, fuel, or compression systems. Here's a breakdown of common causes and diagnostic steps:

  1. Ignition System Check:

    • Spark Plug: The most common cause. A worn, fouled, or damaged spark plug in cylinder 2 can easily cause a misfire. Inspect the plug for signs of wear, carbon buildup, or damage. It's often recommended to replace all spark plugs if they are due for maintenance.
    • Ignition Coil: The ignition coil for cylinder 2 could be failing. A simple diagnostic step is to swap the coil from cylinder 2 with a coil from a different cylinder (e.g., cylinder 1 or 3). If the misfire code then moves to the new cylinder (e.g., P0301 or P0303), you've identified a faulty coil.

  2. Fuel System Check:

    • Fuel Injector: A clogged or faulty fuel injector for cylinder 2 can prevent proper fuel delivery, leading to a misfire. This is less common than ignition issues but still possible. Fuel injector cleaner can sometimes help, but a failing injector may need replacement.

  3. Engine Compression:

    • Low Compression: If the spark and fuel systems check out, a loss of compression in cylinder 2 could be the culprit. This can be due to issues like worn piston rings, a faulty valve, or a head gasket problem. A compression test would be necessary to diagnose this.

  4. Vacuum Leaks:

    • While less direct for a single-cylinder misfire, a significant vacuum leak near cylinder 2 could potentially lean out the air-fuel mixture enough to cause a misfire.

When to See a Shop: If you've checked or replaced the spark plug and ignition coil for cylinder 2 and the misfire persists, it's advisable to take your Mini to a qualified mechanic. Diagnosing fuel injector issues, performing a compression test, or identifying more complex engine problems often requires specialized tools and expertise. Continuing to drive with a persistent misfire can lead to further damage, particularly to the catalytic converter.

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