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2021 M2 Competition - Rough Idle & Check Engine Light (Misfire?)

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David L. · rep 0 · May 22, 4:08 AM · 1 replies · solved · Question

Vehicle: 2021 BMW M2 Competition

My 2021 BMW M2 Competition (F87) with about 40k miles just threw a check engine light and started idling really rough. It feels like it's misfiring, especially at lower RPMs. I haven't pulled the codes yet, but I'm guessing it's a misfire on one or more cylinders.

Is this common for the S55 engine at this mileage? What's the usual culprit – spark plugs, ignition coils, or something else? Any specific OBD codes I should look out for when I scan it?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:08 AM

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ClearTheCode admin answer:

A rough idle and a check engine light, especially with symptoms of misfiring, are common indicators of an ignition system issue. For your 2021 BMW M2 Competition (F87) with the S55 engine at 40,000 miles, this is a plausible scenario.

Common Culprits for Misfires on S55 Engines:

  1. Spark Plugs: While 40k miles isn't extremely high, aggressive driving or tuning can accelerate spark plug wear. Worn plugs can lead to weak or inconsistent spark, causing misfires.
  2. Ignition Coils: Ignition coils are responsible for generating the high voltage needed for the spark plugs. They can fail individually, leading to misfires on specific cylinders. This is a very common failure point on many BMW engines.
  3. Fuel Injectors: Less common than plugs or coils, but a faulty fuel injector (stuck open or closed, or spraying poorly) can also cause a misfire on a specific cylinder.

OBD Codes to Look Out For:

When you scan your vehicle, you'll likely see codes in the P030x range:

  • P0300: Random/Multiple Cylinder Misfire Detected
  • P0301 - P0306: Cylinder 1 Misfire Detected (P0302 for cylinder 2, etc.)

Steps for Diagnosis & DIY:

  • Scan for Codes: Use an OBD-II scanner to pull the exact fault codes. This will tell you which cylinder(s) are misfiring.
  • Swap Coils: If a specific cylinder misfire (e.g., P0303) is detected, you can try swapping the ignition coil from the misfiring cylinder to a known good cylinder. If the misfire code follows the coil, you've found the culprit.
  • Inspect Spark Plugs: If swapping coils doesn't resolve it, or if you suspect plugs, remove and inspect the spark plugs from the affected cylinders. Look for signs of wear, fouling, or damage.
  • Replace in Sets: It's often recommended to replace spark plugs in sets (all 6 for the S55) and, if one coil fails, consider replacing all coils, especially if they are original and have similar mileage.

When to See a Shop:

If you're not comfortable performing these diagnostic steps, or if replacing plugs and coils doesn't resolve the issue, it's time to visit a BMW specialist. They have advanced diagnostic tools to test fuel injectors, check compression, and identify more complex issues within the S55 engine.

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