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Rough Idle and Misfire on 2017 Ram 1500 Rebel 5.7L Hemi - P030x Codes

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

Vehicle: 2017 Ram 1500 Rebel

My 2017 Ram 1500 Rebel, 5.7L Hemi, has developed a really rough idle and feels like it's misfiring, especially when cold. The check engine light came on, and my scanner is showing multiple P030x codes – specifically P0301, P0303, and P0305, indicating misfires on cylinders 1, 3, and 5.

It's got about 90,000 miles on it. I've heard about the MDS system causing issues, but could it be something simpler like spark plugs or coil packs? I haven't changed the plugs in a while.

Any common issues with these Hemi engines that would cause misfires on multiple cylinders on one bank? What's the best way to approach diagnosing this?

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

Misfires on multiple cylinders, especially on one bank (cylinders 1, 3, 5 are on the passenger side of a Hemi), can be indicative of a few common issues on your 2017 Ram 1500 5.7L Hemi. Given the mileage, it's a good time to investigate.

Here's a breakdown of potential causes and diagnostic steps:

  1. Spark Plugs and Coil Packs: Start with the basics. If spark plugs haven't been replaced around the 60,000-mile mark, they are a prime suspect. Worn plugs can lead to weak or inconsistent spark. While individual coil packs usually cause a single cylinder misfire, a failing coil pack harness or a shared power/ground issue could affect multiple. You can try swapping coil packs between misfiring and non-misfiring cylinders to see if the code follows the coil.
  2. Fuel Injectors: Clogged or failing fuel injectors on those cylinders could cause a lean misfire. You can test injector resistance or listen to them with a stethoscope to ensure they are clicking. Fuel injector cleaner might offer a temporary fix, but a professional cleaning or replacement might be needed.
  3. Intake Manifold Gasket Leak: A vacuum leak on one side of the intake manifold could affect multiple cylinders on that bank, leading to a lean condition and misfires. You can spray carb cleaner around the intake manifold gasket area while the engine is running; if the idle changes, you've found a leak.
  4. MDS (Multi-Displacement System) Lifter Issues: The Hemi's MDS system can sometimes lead to lifter failure, which can cause misfires. This is often accompanied by a ticking noise from the engine. If lifters are failing, it's a more serious repair. However, typically, this would affect one cylinder more severely initially.
  5. Compression Test: If all else fails, a compression test on the affected cylinders can rule out internal engine issues like worn piston rings or valve problems.

When to See a Shop:

  • If replacing spark plugs and swapping coil packs doesn't resolve the issue.
  • If you suspect a fuel injector problem and don't have the tools to test them properly.
  • If you hear a persistent ticking noise from the engine, which could indicate a lifter issue.
  • If you're uncomfortable performing a compression test or diagnosing vacuum leaks. A professional can quickly pinpoint the exact cause using specialized diagnostic equipment and perform necessary repairs, especially if it points to internal engine components.
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