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2020 Cadillac Escalade Rough Idle & Misfire Codes P0301, P0303

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Emily N. · rep 0 · May 22, 3:56 AM · 1 replies · solved · Question

Vehicle: 2020 Cadillac Escalade ESV

Hi all,

My 2020 Cadillac Escalade ESV (6.2L V8) with about 45,000 miles has developed a really rough idle and feels like it's misfiring. The Check Engine Light came on, and when I scanned it, I got P0301 (Cylinder 1 Misfire Detected) and P0303 (Cylinder 3 Misfire Detected) codes.

It's most noticeable when I'm stopped at a light or in park. The whole vehicle shakes a bit, and there's a noticeable loss of power when accelerating. I haven't done any major maintenance recently besides regular oil changes. I'm hoping it's something simple like spark plugs or coils, but I'm open to other suggestions.

Any ideas on what might be causing these multiple cylinder misfires on my Escalade? Thanks for any help!

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

Multiple cylinder misfire codes (P030x) on your 2020 Cadillac Escalade ESV indicate that the engine control module (ECM) is detecting a lack of combustion in specific cylinders. While P0301 and P0303 point to cylinders 1 and 3, it's important to consider common causes that can affect multiple cylinders or lead to a cascade effect.

Here are the most common culprits for misfires:

  1. Ignition System:
    • Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. At 45,000 miles, they might be due for inspection or replacement, especially if you do a lot of stop-and-go driving.
    • Ignition Coils: A failing ignition coil for cylinder 1 and/or 3 would directly cause these codes. Sometimes, one failing coil can put stress on others.
    • Spark Plug Wires (if applicable): While less common on modern engines, damaged wires can prevent spark.
  2. Fuel System:
    • Fuel Injectors: Clogged or faulty fuel injectors for cylinders 1 and 3 would prevent proper fuel delivery. This is a significant possibility.
    • Low Fuel Pressure: A failing fuel pump or clogged fuel filter could lead to insufficient fuel pressure, causing multiple cylinders to misfire, though usually, this would affect more cylinders or be more random.
  3. Air/Vacuum Leaks:
    • Intake Manifold Gasket/Vacuum Hoses: A vacuum leak around the intake manifold or a cracked vacuum hose can introduce unmetered air, leaning out the air/fuel mixture and causing misfires, often affecting multiple cylinders.
  4. Engine Mechanical Issues:
    • Low Compression: Worn piston rings, valves, or a blown head gasket could lead to low compression in a cylinder, causing a misfire. This is less common at 45,000 miles but possible.
    • PCV System: A clogged or faulty PCV (Positive Crankcase Ventilation) valve can sometimes lead to vacuum issues or oil consumption that affects combustion.

What to do:

  • Inspect Spark Plugs and Coils: If you're comfortable, you can swap the ignition coils from cylinder 1 and 3 with known good cylinders (e.g., 2 and 4). If the misfire codes follow the coils, you've found the issue. Otherwise, inspect the spark plugs.
  • Check for Vacuum Leaks: Listen for hissing sounds around the engine bay, especially near the intake manifold and vacuum lines.

When to see a shop:

If swapping coils doesn't resolve the issue, or if you're not comfortable performing these checks, it's best to take your Escalade to a qualified technician. They can perform a more thorough diagnosis, including:

  • Fuel pressure tests.
  • Injector pulse tests.
  • Compression tests.
  • Smoke tests for vacuum leaks.
  • Advanced scanner diagnostics to monitor live misfire data and fuel trims.
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