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Rough Idle & Misfires on 2020 Mirage - Time for New Plugs?

0

Steve N. · rep 0 · May 22, 5:36 AM · 1 replies · solved · Question

Vehicle: 2020 Mitsubishi Mirage G4 ES

My 2020 Mitsubishi Mirage G4 ES, with around 45,000 miles, has started to develop a rough idle lately. It feels a bit sluggish, and I've noticed a slight hesitation when accelerating, especially from a stop. The check engine light came on briefly a couple of times but then went off on its own.

I'm thinking it might be time for new spark plugs, but I wanted to get some opinions from the community. Is this a common issue for the Mirage at this mileage? What kind of plugs should I use (OEM vs. aftermarket), and is it a straightforward DIY job for someone with basic mechanical skills?

I'd like to tackle this myself if possible to save on labor costs. Any tips or warnings would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:36 AM

0

ClearTheCode admin answer:

It's definitely possible that your rough idle, sluggishness, and intermittent check engine light on your 2020 Mitsubishi Mirage G4 ES at 45,000 miles are symptoms of worn spark plugs. While 45k miles might seem a bit early for some modern iridium plugs, driving conditions and fuel quality can accelerate wear. The Mirage's 3-cylinder engine can be quite sensitive to ignition system health.

Common Causes & Diagnostics:

  • Worn Spark Plugs: Over time, the electrode wears down, increasing the gap and requiring more voltage to fire, leading to misfires.
  • Failing Ignition Coils: Less common at this mileage, but a weak coil can also cause misfires.
  • Fuel System Issues: Clogged fuel injectors can also cause similar symptoms, though less likely to be intermittent.
  • OBD Codes: If the check engine light came on, even briefly, it likely stored a code. Common misfire codes include P0300 (random/multiple cylinder misfire) or P0301, P0302, P0303 (specific cylinder misfire for cylinders 1, 2, or 3 respectively).

DIY Spark Plug Replacement Steps:

  1. Gather Tools: You'll need a spark plug socket (usually 14mm or 16mm, thin-walled), ratchet, extensions, torque wrench, dielectric grease, and anti-seize compound.
  2. Disconnect Battery: For safety, disconnect the negative terminal of your car battery.
  3. Access Plugs: On the Mirage's 3-cylinder engine, the ignition coils are usually easily accessible on top of the engine. Disconnect the electrical connector from each coil and remove the bolt holding it down.
  4. Remove Coils: Carefully pull each ignition coil straight up to remove it.
  5. Remove Spark Plugs: Use your spark plug socket and extension to reach down into the cylinder head and carefully unscrew each spark plug. Inspect the old plugs for signs of wear, oil, or carbon buildup.
  6. Install New Plugs: It's highly recommended to use OEM Mitsubishi spark plugs or high-quality iridium equivalents (e.g., NGK Iridium IX or Denso Iridium Long Life) specified for your vehicle. Apply a small amount of anti-seize to the threads and a dab of dielectric grease inside the coil boot. Hand-thread the new plugs to avoid cross-threading, then torque them to the manufacturer's specifications (usually around 15-20 ft-lbs).
  7. Reinstall Coils & Connectors: Push the ignition coils back into place, secure them with their bolts, and reconnect the electrical connectors.
  8. Reconnect Battery: Reconnect the negative battery terminal.

When to See a Shop:

  • If replacing the spark plugs doesn't resolve the issue, or if the check engine light returns with persistent misfire codes.
  • If you're uncomfortable with the process, don't have the correct tools, or suspect a more complex issue like a failing ignition coil or fuel injector.
  • If you're unable to retrieve the OBD codes, a shop can perform a more thorough diagnostic.
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