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2017 Ram 1500 Rebel - Rough Idle & Misfire Codes P0301, P0303

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Mike T. · rep 0 · May 22, 3:30 AM · 1 replies · solved · Question

Vehicle: 2017 Ram 1500 Rebel

Hey everyone,

My 2017 Ram 1500 Rebel (5.7L Hemi) with about 70,000 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 and P0303, indicating misfires on cylinders 1 and 3.

It's most noticeable when I'm stopped at a light or in park. When driving, it feels a bit sluggish, but the misfires are less apparent. I've heard about spark plugs, coil packs, and even lifter issues with these Hemis.

What's the most likely culprit here, especially with two specific cylinders misfiring? Any tips on troubleshooting before I start throwing parts at it?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:30 AM

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ClearTheCode admin answer:

Experiencing P0301 and P0303 (misfires on cylinders 1 and 3) on your 2017 Ram 1500 Rebel's 5.7L Hemi is a common issue that can stem from several sources. Since you have specific cylinder codes, troubleshooting can be more focused.

  1. Ignition System:
    • Spark Plugs: These are the most common cause. Hemi engines are known to be sensitive to spark plug condition. If they haven't been replaced recently (recommended around 30k-60k miles), worn plugs are a prime suspect. Check the plugs from cylinders 1 and 3 for fouling or damage.
    • Ignition Coils: A failing ignition coil pack for cylinder 1 or 3 would directly cause a misfire. You can often swap coils between a misfiring cylinder and a known good cylinder to see if the misfire code follows the coil.
  2. Fuel System:
    • Fuel Injectors: A clogged or faulty fuel injector for cylinder 1 or 3 would prevent proper fuel delivery. You can test injector resistance or listen to them with a stethoscope for clicking sounds (indicating they're firing).
  3. Compression Issues:
    • Valve Train/Lifters: The 5.7L Hemi is unfortunately known for potential lifter and camshaft issues, especially with higher mileage. A collapsed lifter or worn cam lobe would lead to poor compression and a persistent misfire. This is a more serious and costly repair.
    • Head Gasket: Less common for specific cylinder misfires without other symptoms (like coolant loss or white smoke), but a failing head gasket could also cause compression loss.

What to do:

  • Swap Coils: Move the ignition coil from cylinder 1 to cylinder 2 (or another good cylinder) and the coil from cylinder 3 to cylinder 4. Clear the codes and drive. If the misfire codes change to P0302 and P0304, you've identified faulty coils.
  • Inspect Spark Plugs: Remove and inspect the spark plugs from cylinders 1 and 3. Look for signs of wear, oil fouling, or unusual deposits.
  • Check for Vacuum Leaks: A vacuum leak near the intake manifold could affect specific cylinders, though it's less common for only two non-adjacent cylinders.

When to see a shop:

If swapping coils and inspecting plugs doesn't resolve the issue, or if you suspect a fuel injector problem, it's best to consult a professional. If the misfire persists after these checks, a compression test and further diagnosis for lifter/camshaft issues will be necessary, which requires specialized tools and expertise.

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