2018 Challenger R/T - P0302 Misfire & Rough Idle

Hello Chris,

A P0302 code specifically points to a misfire detected in cylinder 2. Since you've already swapped the spark plug and coil pack without the code moving, that's excellent diagnostic work, as it rules out those common culprits for that specific cylinder.

Here are the next steps to diagnose your 2018 Challenger R/T's P0302:

1. Check Fuel Injector:

   • Listen: Use a mechanic's stethoscope (or a long screwdriver to your ear) to listen to the fuel injector on cylinder 2. Compare its clicking sound to adjacent cylinders. A weak or absent click could indicate a faulty injector.
   • Swap Injector: If possible, swap the fuel injector from cylinder 2 to another cylinder (e.g., cylinder 4). Clear the code and drive the vehicle. If the misfire code changes to P0304, you've found your faulty injector.

2. Perform a Compression Test:

   • A misfire can also be caused by low compression in a cylinder. This could be due to a faulty valve, head gasket issue, or piston ring problem. A compression test will measure the pressure in cylinder 2 and compare it to the others.

3. Check for Vacuum Leaks:

   • While less common for a single-cylinder misfire, a vacuum leak near cylinder 2 could lean out the fuel mixture enough to cause a misfire. Inspect vacuum lines and intake manifold gaskets in that area.

4. Inspect Wiring:

   • Check the wiring harness and connector for the cylinder 2 coil pack and fuel injector. Look for any frayed wires, corrosion, or loose connections.

When to See a Shop: If after checking the fuel injector and performing a compression test you still haven't identified the issue, it's time to take your Challenger to a qualified mechanic. They have specialized diagnostic tools to check fuel pressure, injector pulse, and perform more in-depth tests like a leak-down test, which can pinpoint internal engine issues more precisely. Continuing to drive with a persistent misfire can damage your catalytic converter.