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2020 Outlander Sport - Rough Idling and P0301 Code

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Sarah K. · rep 0 · May 25, 4:05 AM · 1 replies · solved · Question

Vehicle: 2020 Mitsubishi Outlander Sport ES

Hi all,

I'm having an issue with my 2020 Mitsubishi Outlander Sport ES. It has about 45,000 miles on it. Lately, it's developed a really rough idle, especially when cold, and sometimes feels a bit sluggish during acceleration. The check engine light came on, and my scanner pulled a P0301 code, indicating a misfire in cylinder 1.

I've read that this could be spark plugs, ignition coils, or even fuel injectors. I replaced the spark plugs about 10,000 miles ago, so I'm hoping it's not them already. Could it be something simpler like a vacuum leak or a bad sensor?

Any specific things I should check first for a P0301 on this model? I'm trying to avoid just throwing parts at it.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:05 AM

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ClearTheCode admin answer:

A P0301 code on your 2020 Mitsubishi Outlander Sport ES signifies a misfire detected in cylinder #1. This means the engine's computer isn't seeing the expected combustion in that cylinder. While spark plugs are a common cause, especially if they are old, your recent replacement suggests other areas need attention.

Common Causes for P0301:

  1. Ignition System:
    • Ignition Coil: A faulty ignition coil for cylinder #1 is a very common culprit. The coil provides the high voltage for the spark plug.
    • Spark Plug: Even if recently replaced, a defective or fouled plug can cause a misfire. Ensure the correct gap and type were used.
    • Spark Plug Wire (if applicable): Though less common on newer engines, a damaged wire can interrupt spark delivery.
  2. Fuel System:
    • Fuel Injector: A clogged, dirty, or faulty fuel injector for cylinder #1 won't deliver enough fuel, leading to a lean misfire.
    • Low Fuel Pressure: While less likely to be cylinder-specific, overall low fuel pressure can cause misfires across multiple cylinders.
  3. Air/Compression System:
    • Vacuum Leak: A vacuum leak near cylinder #1 or in the intake manifold can lean out the air-fuel mixture for that cylinder.
    • Low Compression: Worn piston rings, a bent valve, or a faulty head gasket can cause low compression in cylinder #1, preventing proper combustion.
    • EGR Valve Issues: A sticking EGR valve can sometimes cause misfires, though typically not cylinder-specific.

Diagnostic Steps:

  1. Swap Ignition Coil: Move the ignition coil from cylinder #1 to another cylinder (e.g., cylinder #2). Clear the code and drive. If the misfire moves to cylinder #2 (P0302), the coil is bad.
  2. Swap Spark Plug: Similarly, swap the spark plug from cylinder #1 to another cylinder. If the misfire follows the plug, the plug is the issue.
  3. Fuel Injector Test: Listen to the injector with a stethoscope to ensure it's clicking. You can also swap injectors between cylinders (though more involved) to see if the misfire moves.
  4. Compression Test: If the above steps don't identify the problem, perform a compression test on cylinder #1 and compare it to others. This will indicate if there's an internal engine issue.
  5. Vacuum Leak Check: Use a smoke machine or spray unlit propane around the intake manifold area while the engine is running to detect vacuum leaks.

When to See a Shop: If you're unable to diagnose the issue with these steps, or if a compression test indicates an internal engine problem, it's crucial to take your vehicle to a professional mechanic. Continued driving with a misfire can damage the catalytic converter.

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