Misfire and Rough Idle on 2019 Ram 1500 5.7L HEMI - DIY Spark Plugs?

ClearTheCode admin answer:

A P0301 code (misfire on cylinder 1) on your 2019 Ram 1500 5.7L HEMI with 80,000 miles strongly suggests that it's time for new spark plugs. The 5.7L HEMI engine does indeed use 16 spark plugs – two per cylinder – which is a common design feature for these engines to enhance combustion efficiency.

DIY Spark Plug Replacement:

1. Tools Needed:

   • Spark plug socket (typically 5/8" or 16mm, thin-walled, with a rubber insert to hold the plug).
   • Ratchet and various extensions (3", 6", 10" are helpful).
   • Torque wrench (critical for proper plug installation).
   • Dielectric grease (for coil boots) and anti-seize compound (for plug threads, though many modern plugs come pre-coated).
   • Gapper tool (if plugs aren't pre-gapped, but typically they are).
   • Flathead screwdriver or trim tool to release coil pack connectors.

2. Procedure Overview:

   • Access: The coils and plugs are under the engine cover. You'll need to remove the engine cover and potentially some air intake components to gain access, especially on the passenger side.
   • Coil Packs: Each cylinder has one ignition coil pack that fires both plugs for that cylinder. Disconnect the electrical connector, then unbolt the coil pack (usually one bolt) and pull it straight up to remove.
   • Spark Plugs: Use your spark plug socket and extension to remove the old plugs. Be careful not to cross-thread when installing new ones. Always start by hand to ensure proper threading before using a ratchet.
   • Torque: This is crucial. Over-tightening can damage the cylinder head, while under-tightening can lead to misfires or plugs backing out. Consult your service manual for the exact torque specification (usually around 13-15 ft-lbs for these plugs).

3. Common Pitfalls:

   • Cross-threading: Always start plugs by hand.
   • Incorrect Torque: Use a torque wrench.
   • Damaging Wires/Coils: Be gentle when disconnecting connectors and pulling coils.
   • Dropping Plugs: Don't drop new plugs, as this can close the gap or crack the ceramic.

Ignition Coils: Given your mileage and a specific misfire code (P0301), it's generally recommended to replace the ignition coil on the affected cylinder (Cylinder 1) when you do the spark plugs. While not strictly necessary for all 16, replacing the faulty one is good practice. If you want to be proactive, you could replace all 8 coils (one per cylinder) as preventative maintenance, but it adds significant cost. For a single misfire, start with the plug and the corresponding coil.

When to See a Shop: If you're uncomfortable with the process, especially the delicate torque requirements or accessing certain plugs, a professional shop can perform the service efficiently. If replacing the plug and coil for cylinder 1 doesn't resolve the P0301 code, then the issue might be deeper (e.g., fuel injector, valve train, compression), requiring further diagnostic work from a qualified technician.