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2017 XT5 Rough Idle & Misfire Codes P0300, P0301

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David L. · rep 0 · May 22, 3:56 AM · 1 replies · solved · Question

Vehicle: 2017 Cadillac XT5 Luxury

My 2017 Cadillac XT5 Luxury has developed a really rough idle, especially when cold, and the Check Engine Light came on. I scanned it and got P0300 (Random/Multiple Cylinder Misfire Detected) and P0301 (Cylinder 1 Misfire Detected).

The car feels a bit sluggish under acceleration, and the idle shakes the whole car. I've heard about spark plug issues or coil packs on these engines. Could it be something else? I'm trying to figure out if this is something I can tackle myself or if it needs a shop immediately.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:56 AM

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ClearTheCode admin answer:

The P0300 and P0301 codes on your 2017 Cadillac XT5 Luxury indicate that your engine is experiencing misfires, specifically on Cylinder 1 and potentially other cylinders randomly. This can lead to rough idle, reduced power, and decreased fuel economy.

Here are the most common causes for misfire codes:

  1. Ignition System:
    • Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. If Cylinder 1's plug is bad, it directly causes P0301. If multiple are worn, it can lead to P0300.
    • Ignition Coils: A failing ignition coil for Cylinder 1 would cause P0301. If other coils are also weak, it could contribute to P0300. You can often swap coils between cylinders to see if the misfire moves.
  2. Fuel System:
    • Fuel Injector: A clogged or faulty fuel injector for Cylinder 1 would prevent it from getting enough fuel, causing a misfire. You can test injector resistance or listen to them with a stethoscope.
    • Low Fuel Pressure: A failing fuel pump or clogged fuel filter could lead to insufficient fuel delivery to all cylinders, resulting in random misfires (P0300).
  3. Air/Vacuum Leaks: Unmetered air entering the intake manifold can lean out the air-fuel mixture, causing misfires. Check for cracked vacuum hoses, a loose intake manifold, or a faulty PCV valve.
  4. Engine Mechanical Issues:
    • Low Compression: Worn piston rings, valves, or a head gasket leak can cause low compression in a cylinder, leading to misfires. This is less common but a serious issue.
    • Timing Issues: A stretched timing chain or faulty VVT (Variable Valve Timing) components can throw off engine timing, causing misfires.

When to See a Shop:

  • If swapping ignition coils or replacing spark plugs doesn't resolve the issue.
  • If you suspect a fuel injector problem, as testing and replacement can be more involved.
  • If you hear unusual engine noises or suspect a mechanical issue like low compression or timing problems, which require specialized tools and expertise.
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