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2018 Challenger R/T Misfire and Rough Idle - P030X Codes

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Kim L. · rep 0 · May 22, 5:39 AM · 1 replies · solved · Question

Vehicle: 2018 Dodge Challenger R/T

Hey everyone,

I'm having some trouble with my 2018 Dodge Challenger R/T, 5.7L Hemi. Lately, it's developed a really rough idle, especially when cold, and I can feel it misfiring under light acceleration. The check engine light came on a few days ago and it's been pretty consistent.

I hooked up my OBD-II scanner and it's showing multiple misfire codes: P0301 (Cylinder 1 Misfire Detected), P0303 (Cylinder 3 Misfire Detected), and P0300 (Random/Multiple Cylinder Misfire Detected). Sometimes it feels like it's going to stall at stop lights.

Has anyone experienced this with their Hemi? What should I be looking at first? Plugs, coils, injectors? Any advice would be greatly appreciated before I start throwing parts at it.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:39 AM

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ClearTheCode admin answer:

Dealing with multiple misfire codes like P0300, P0301, and P0303 on your 2018 Dodge Challenger R/T can be frustrating, but it's a common issue with several potential causes. Here's a diagnostic approach:

  1. Check for Common Causes:

    • Spark Plugs: These are a frequent culprit. Hemi engines can be hard on plugs. Inspect them for wear, fouling, or cracks. If they haven't been replaced in a while (e.g., over 30,000-50,000 miles), consider replacing them, especially if you're seeing misfires on specific cylinders.
    • Ignition Coils: A failing ignition coil can cause a misfire. You can try swapping coils between a misfiring cylinder and a non-misfiring one to see if the code follows the coil. This helps isolate a faulty coil.
    • Fuel Injectors: Clogged or faulty fuel injectors can lead to lean misfires. You might consider running a quality fuel system cleaner or having the injectors professionally tested.
    • Vacuum Leaks: A vacuum leak can cause a lean condition and rough idle, leading to misfires. Check all vacuum lines and intake manifold gaskets for cracks or disconnections.

  2. Advanced Diagnostics:

    • Compression Test: If basic checks don't reveal the issue, a compression test can identify internal engine problems like a bad valve or head gasket, which would definitely cause misfires.
    • Fuel Pressure Test: Low fuel pressure can cause multiple misfires across cylinders. Check your fuel pump and fuel filter.
    • PCV Valve: A stuck PCV valve can also contribute to vacuum issues and oil consumption, indirectly affecting combustion.

  3. When to See a Shop:

    • If you've checked the basic components (plugs, coils, obvious vacuum leaks) and the problem persists.
    • If you lack the tools or expertise for a compression or fuel pressure test.
    • If the misfires are accompanied by unusual noises, smoke from the exhaust, or significant power loss, as this could indicate a more serious engine problem requiring professional attention immediately to prevent further damage.
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