2018 Charger R/T Rough Idle and Misfires - CEL On

ClearTheCode admin answer:

A rough idle and misfires, especially with a Check Engine Light (CEL) on, are common symptoms that point to several potential issues in your 2018 Dodge Charger R/T's 5.7L HEMI engine. It's crucial to address this promptly to prevent further damage.

1. Get the OBD-II Codes Read:

• This is the first and most important step. Most auto parts stores offer free code reading services. Common codes for these symptoms include: * P030x (e.g., P0301, P0302, etc.): Misfire detected in cylinder X. * P0300: Random/multiple cylinder misfire detected. * P0420/P0430: Catalyst System Efficiency Below Threshold (Bank 1/Bank 2), which could be a secondary issue if misfires are prolonged.

2. Common Causes & Diagnostics:

• Ignition System: * Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. Given your mileage (75k), they might be due for replacement if not done recently. * Ignition Coils: A failing ignition coil for a specific cylinder will cause a misfire in that cylinder. If you have a P030x code, swapping the coil to another cylinder can help diagnose if the coil is the culprit.
• Fuel System: * Fuel Injectors: A clogged or failing fuel injector can cause a cylinder to run lean or rich, leading to misfires. * Fuel Pressure: Low fuel pressure from a failing fuel pump or clogged fuel filter can affect overall engine performance.
• Air/Vacuum Leaks: Unmetered air entering the engine can cause a lean condition and rough idle. Check vacuum lines and intake manifold gaskets.
• PCV Valve: A faulty PCV valve can cause vacuum leaks or oil consumption, affecting idle quality.
• Oxygen Sensors: While less likely to be the primary cause of misfires, faulty O2 sensors can affect fuel trim and lead to performance issues and potentially trigger catalytic converter codes.
• Catalytic Converter: If misfires persist for a long time, unburnt fuel can damage the catalytic converter, leading to codes like P0420/P0430. However, the misfire is usually the root cause, not the converter itself initially.

3. When to See a Professional Shop:

• Persistent CEL: If the CEL is flashing, it indicates a severe misfire that could be damaging the catalytic converter, and you should stop driving immediately and get it towed.
• Lack of Diagnostic Tools: If you don't have the tools or expertise to diagnose and replace components like coils, plugs, or injectors.
• Complex Issues: If basic diagnostics (like spark plugs/coils) don't resolve the issue, or if multiple codes appear, a professional can perform more in-depth diagnostics (e.g., compression test, fuel pressure test, smoke test for vacuum leaks).
• Safety Concerns: Any significant loss of power, stalling, or unusual noises warrant immediate professional attention.

Start by getting those codes read. That will narrow down the possibilities significantly.