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2018 Outlander SEL - Rough Idle and Check Engine Light On

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Mike T. · rep 0 · May 24, 3:11 PM · 1 replies · solved · Question

Vehicle: 2018 Mitsubishi Outlander SEL

Hey everyone, I've got a problem with my 2018 Mitsubishi Outlander SEL. Lately, it's been idling really rough, especially when I'm stopped at a light or in park. The whole car shakes a bit, and it feels like it might stall. A few days ago, the check engine light came on and hasn't gone off since.

I haven't noticed any major power loss while driving, but the rough idle is definitely concerning. It seems to happen more when the engine is warm, but it's not consistent. Sometimes it's barely noticeable, other times it's quite pronounced.

Has anyone experienced something similar with their Outlander? Any ideas what could be causing this? I'm hoping it's something simple before I have to take it to the dealership.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 3:11 PM

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ClearTheCode admin answer:

Rough idle accompanied by a Check Engine Light (CEL) on your 2018 Mitsubishi Outlander SEL typically points to an issue within the engine's combustion or air/fuel delivery system. Here's a breakdown of common causes and steps you can take:

  1. Retrieve OBD-II Codes: The first and most crucial 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 loan at auto parts stores. Common codes for rough idle and misfires include:

    • P0300: Random/Multiple Cylinder Misfire Detected
    • P0301 - P0304: Cylinder 1-4 Misfire Detected (specific to which cylinder is misfiring)

  2. Common Causes for Misfires/Rough Idle:

    • Ignition System: Worn spark plugs, faulty ignition coils, or damaged spark plug wires (less common on modern engines) are frequent culprits. Over time, spark plugs degrade, leading to inefficient combustion.
    • Fuel System: Clogged fuel injectors can prevent a cylinder from getting enough fuel, causing a misfire. A weak fuel pump or a clogged fuel filter can also lead to fuel delivery issues, though less likely to cause specific cylinder misfires.
    • Air Intake/Vacuum Leaks: Unmetered air entering the engine due to a vacuum leak (e.g., cracked hose, faulty gasket) can disrupt the air-fuel mixture, leading to rough idling.
    • Sensor Issues: A failing Mass Air Flow (MAF) sensor or Oxygen (O2) sensor can send incorrect data to the engine control unit (ECU), causing the engine to run rich or lean and idle poorly.
    • EGR System: A stuck-open Exhaust Gas Recirculation (EGR) valve can cause a vacuum leak and rough idle.

  3. When to See a Shop:

    • If the OBD-II codes indicate a complex issue (e.g., multiple sensor failures, catalytic converter issues).
    • If you're not comfortable performing basic diagnostic checks or repairs yourself.
    • If the issue persists after addressing common problems like spark plugs or ignition coils.
    • If the rough idle is severe, accompanied by significant power loss, or if the CEL is flashing (indicating a severe misfire that could damage the catalytic converter), it's best to have it professionally inspected immediately.
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