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Rough idle and engine light on my 2018 Cooper S - P0302 code

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Melissa G. · rep 0 · May 22, 6:54 AM · 1 replies · solved · Question

Vehicle: 2018 Mini Cooper S

Hey everyone,

I'm having some trouble with my 2018 Mini Cooper S (F56 chassis). Lately, it's developed a really rough idle, especially when I first start it up in the morning or after it's been sitting for a while. It feels like the engine is shaking more than usual, and there's a noticeable drop in power when I accelerate.

The check engine light came on, and I used my OBD-II scanner to pull the code. It's showing P0302, which indicates a misfire in cylinder 2. I'm not sure if this is a common issue with these Minis or what the usual culprits are.

Has anyone experienced this before with their Cooper S? What did you do to fix it? I'm hoping it's something relatively simple I can tackle myself before taking it to a shop. Any advice or diagnostic tips would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:54 AM

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ClearTheCode admin answer:

A P0302 code on your 2018 Mini Cooper S (F56) indicates a misfire specifically detected in cylinder 2. This is a common issue that can stem from several components within the engine's ignition, fuel, or air systems. Addressing it promptly is important to prevent further engine damage.

Here are the common causes and diagnostic steps:

  1. Ignition System Components:

    • Spark Plug: The most common cause. A worn, fouled, or incorrectly gapped spark plug in cylinder 2 can easily cause a misfire. Start by inspecting and potentially replacing the spark plug in cylinder 2.
    • Ignition Coil: The ignition coil for cylinder 2 might be failing. You can often diagnose this by swapping the coil from cylinder 2 with one from a different cylinder (e.g., cylinder 1 or 3). If the misfire code moves to the new cylinder, the coil is faulty.

  2. Fuel System Components:

    • Fuel Injector: A clogged, dirty, or failing fuel injector for cylinder 2 can prevent proper fuel delivery, leading to a misfire. Fuel injector cleaner can sometimes help, but a failing injector will need replacement. This is less common than ignition issues but definitely a possibility.
    • Fuel Pressure: While less likely to cause a single-cylinder misfire, low overall fuel pressure could exacerbate issues. This would typically trigger other codes as well.

  3. Air/Compression Issues:

    • Vacuum Leak: A vacuum leak near cylinder 2 could lean out the air-fuel mixture, causing a misfire. Inspect vacuum lines and intake manifold gaskets for cracks or leaks.
    • Engine Compression: In more severe cases, low compression in cylinder 2 (due to issues like worn piston rings, a faulty valve, or a blown head gasket) can cause a misfire. This is usually diagnosed with a compression test.

When to see a shop:

  • If you've checked and replaced the spark plug and ignition coil for cylinder 2 and the P0302 code persists.
  • If you suspect a fuel injector issue, as this often requires specialized tools for diagnosis and replacement.
  • If you notice any unusual noises, excessive smoke from the exhaust, or a significant loss of power, which could indicate a more serious internal engine problem like low compression.
  • If you're uncomfortable performing the diagnostic steps yourself. A professional can quickly pinpoint the exact cause using advanced diagnostic equipment.
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