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2018 F-150 3.5L EcoBoost Rough Idle & Check Engine Light

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Mike T. · rep 0 · May 24, 1:16 PM · 1 replies · solved · Question

Vehicle: 2018 Ford F-150 Lariat

Hey everyone,

I'm having an issue with my 2018 Ford F-150 Lariat, which has the 3.5L EcoBoost engine. Lately, it's developed a really rough idle, especially when I'm stopped at a light or in park. It feels like the whole truck is shaking a bit more than it should.

To top it off, the Check Engine Light came on a couple of days ago and hasn't gone off. I haven't noticed any significant loss of power while driving, but the rough idle is definitely concerning. Fuel economy might be slightly worse, but it's hard to tell for sure.

Has anyone else experienced something similar with their 3.5L EcoBoost F-150? I'm trying to figure out if this is a common problem or what might be causing it before I take it into the shop. Any advice on what to check first would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 1:16 PM

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ClearTheCode admin answer:

It sounds like your 2018 Ford F-150 with the 3.5L EcoBoost is experiencing a common issue related to engine misfires or fuel/air mixture problems. The rough idle and Check Engine Light (CEL) are strong indicators that your engine control unit (ECU) has detected an anomaly.

Here's a breakdown of potential causes and steps:

  1. Get the OBD-II Codes Read: This is the crucial first step. Most auto parts stores offer free code reading services. Common codes for these symptoms include:

    • P0300 (Random/Multiple Cylinder Misfire Detected)
    • P030X (Cylinder X Misfire Detected) - where X is the cylinder number (e.g., P0301 for cylinder 1).
    • P0171 (System Too Lean Bank 1) or P0174 (System Too Lean Bank 2) - indicating an air leak or fuel delivery issue.

  2. Common Causes for Misfires/Rough Idle in EcoBoost Engines:

    • Spark Plugs: These engines are hard on spark plugs. Worn or fouled plugs are a very common cause of misfires, especially after 60,000-80,000 miles. They are relatively easy to replace.
    • Ignition Coils: A failing ignition coil for a specific cylinder can cause a misfire. The OBD-II code P030X will pinpoint the cylinder.
    • Vacuum Leaks: Leaks in vacuum lines, the PCV valve, or intake manifold gaskets can lead to unmetered air entering the engine, causing a lean condition and rough idle.
    • Fuel Injectors: Clogged or faulty fuel injectors can cause a cylinder to run lean or misfire. This is less common but possible.
    • Carbon Buildup: Direct injection engines like the EcoBoost can accumulate carbon on the intake valves over time, which can affect airflow and combustion efficiency.

  3. When to See a Shop:

    • If you're not comfortable performing DIY diagnostics or repairs, or if the problem persists after checking basic components like spark plugs.
    • If the CEL is flashing, this indicates a severe misfire that could damage the catalytic converter, and you should stop driving immediately and have it towed.
    • If the codes point to more complex issues like P0171/P0174, which can be harder to diagnose without specialized tools to check for vacuum leaks or fuel pressure.
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