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2018 Tucson 2.0L Misfire - P0302 and Rough Idle

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Mike T. · rep 0 · May 24, 1:21 PM · 1 replies · solved · Question

Vehicle: 2018 Hyundai Tucson SE 2.0L

Hey everyone,

My 2018 Hyundai Tucson SE with the 2.0L engine has developed a pretty frustrating issue lately. The check engine light came on, and the car started to idle really rough, especially when cold. It feels like it's struggling to maintain power at lower speeds too.

I managed to get it scanned, and it's throwing a P0302 code, which indicates a misfire in cylinder 2. I'm not super mechanically inclined, but I'm trying to figure out if this is something I can tackle myself or if it's best to take it straight to a shop.

Has anyone experienced this specific issue with their Tucson? What were the common culprits you found? Any advice on where to start troubleshooting would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 1:21 PM

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ClearTheCode admin answer:

A P0302 code for a cylinder 2 misfire on your 2018 Hyundai Tucson SE 2.0L is a common diagnostic issue. It means the engine's computer detected that cylinder #2 is not contributing power as expected. Here's a breakdown of potential causes and steps you can take:

  1. Verify the Code and Symptoms: First, ensure the code is consistent. Sometimes a single misfire can trigger the CEL. If the rough idle and misfire are constant, it's a more pressing issue.

  2. Common Causes for Misfires (P0302):

    • Ignition System: A faulty spark plug, a bad ignition coil, or a damaged spark plug wire (less common on newer vehicles with coil-on-plug systems).
    • Fuel System: A clogged or faulty fuel injector for cylinder #2, or issues with fuel pressure.
    • Air/Vacuum Leaks: A vacuum leak near cylinder #2 or the intake manifold can lean out the air/fuel mixture, causing a misfire.
    • Engine Mechanical: Low compression in cylinder #2 due to worn piston rings, a bad valve, or a blown head gasket. This is less common but possible.

  3. Diagnostic Steps (DIY Friendly):

    • Check Spark Plug: The easiest first step is to remove the spark plug from cylinder #2 and inspect it. Look for signs of wear, oil fouling, or damage. If it looks bad, replace it (and consider replacing all plugs if they're due for maintenance).
    • Swap Ignition Coil: If the plug looks okay, try swapping the ignition coil from cylinder #2 with a coil from an adjacent cylinder (e.g., cylinder #1 or #3). Clear the code, drive the car, and re-scan. If the misfire code changes to the cylinder you swapped the coil to (e.g., P0301), then the coil is likely bad.
    • Inspect for Vacuum Leaks: Listen for hissing sounds around the intake manifold and vacuum lines. You can also spray a small amount of unlit propane or carb cleaner around these areas (carefully!) – if the idle changes, you've found a leak.

  4. When to See a Shop: If the above steps don't resolve the issue, or if you're uncomfortable performing these diagnostics, it's best to take your Tucson to a qualified mechanic. They have advanced diagnostic tools to test fuel injector pulse, fuel pressure, and perform compression tests. Driving with a persistent misfire can lead to more serious and expensive damage, particularly to your catalytic converter.

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