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Rough Idle and Check Engine Light on 2018 Mirage G4 - Misfire?

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Mike T. · rep 0 · May 25, 4:11 AM · 1 replies · solved · Question

Vehicle: 2018 Mitsubishi Mirage G4 SE

Hi all,

My 2018 Mitsubishi Mirage G4 SE, with about 60,000 miles, has recently started running really rough, especially at idle. The check engine light came on a couple of days ago, and the car feels a bit sluggish when I accelerate.

I haven't had the spark plugs replaced yet, and I'm thinking that might be the culprit. Could a misfiring cylinder cause these symptoms? What's the recommended interval for spark plug replacement on these cars? Any tips for DIY or should I take it to a mechanic?

I'm hoping it's something relatively simple like plugs or coils.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:11 AM

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ClearTheCode admin answer:

It sounds like your 2018 Mitsubishi Mirage G4 is indeed experiencing a misfire, which is very common when spark plugs or ignition coils start to fail. The symptoms you describe—rough idle, sluggish acceleration, and a Check Engine Light (CEL)—are classic indicators.

Here’s a breakdown of what to do:

  1. Retrieve OBD-II Codes: The first step is to get the diagnostic trouble codes (DTCs) from your vehicle's onboard diagnostic system. You can do this with an OBD-II scanner, often available for free use at auto parts stores. Misfire codes typically start with P030X, where X indicates the cylinder (e.g., P0301 for cylinder 1 misfire, P0300 for random/multiple misfires).
  2. Causes of Misfire:
    • Worn Spark Plugs: The most common cause. Over time, electrodes wear down, leading to a weaker spark.
    • Faulty Ignition Coils: Coils can fail, preventing a spark from reaching the plug.
    • Clogged Fuel Injectors: Less common but can starve a cylinder of fuel.
    • Vacuum Leaks: Can cause an imbalanced air/fuel mixture.
    • Low Compression: A more serious engine issue.
  3. Spark Plug Replacement Interval: For your 2018 Mirage G4, Mitsubishi generally recommends spark plug replacement around 60,000 miles for iridium-tipped plugs, which are standard. Given your mileage, this is a prime suspect.
  4. DIY vs. Professional:
    • DIY: Replacing spark plugs on a 3-cylinder Mirage G4 is relatively straightforward for someone with basic mechanical skills. You'll need a spark plug socket, ratchet, and torque wrench. It's also a good idea to inspect or replace the ignition coils if they show signs of wear or if the misfire is specific to one cylinder and follows the coil when swapped.
    • Professional: If you're not comfortable, or if the misfire persists after new plugs/coils, a mechanic can perform a more thorough diagnosis, including compression tests or fuel system checks.

Addressing this promptly is important, as prolonged misfires can damage your catalytic converter.

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