The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

Check Engine Light P0302 on 2018 Mazda 3 - Misfire in Cylinder 2?

0

Mike T. · rep 0 · May 25, 3:36 AM · 1 replies · solved · Question

Vehicle: 2018 Mazda 3 Touring

Hi folks, my 2018 Mazda 3 Touring (2.5L engine, automatic) just threw a check engine light. I pulled the code with my OBD-II scanner, and it's P0302 – Misfire Detected in Cylinder 2. The car feels a bit rough at idle, and I've noticed a slight hesitation when accelerating.

I'm thinking it could be a spark plug or an ignition coil. The car has about 70,000 miles on it, and I haven't changed the spark plugs yet. Is this a common issue for this model year? Any advice on troubleshooting this myself before taking it to a mechanic? What's the typical maintenance schedule for plugs on these Skyactiv engines?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:36 AM

0

ClearTheCode admin answer:

A P0302 code indicates a misfire in cylinder 2, which is a common diagnostic trouble code. Given your mileage, it's highly probable that the issue is related to the ignition system, specifically spark plugs or ignition coils. Mazda recommends spark plug replacement for Skyactiv engines typically around 75,000 miles, so you're right in that timeframe.

Here's a systematic approach to diagnose and resolve the P0302 code:

  1. Check Spark Plug:

    • Cause: A worn or fouled spark plug in cylinder 2 is the most common culprit. Over time, the electrode wears down, leading to a weaker spark.
    • Action: Remove the spark plug from cylinder 2 and inspect it. Look for excessive wear, carbon buildup, or oil fouling. If it looks bad, replace all four spark plugs with OEM-equivalent iridium plugs.

  2. Swap Ignition Coil:

    • Cause: A failing ignition coil can deliver an insufficient spark to the cylinder.
    • Action: If the spark plug looks okay, try swapping the ignition coil from cylinder 2 with a coil from another cylinder (e.g., cylinder 1 or 3). Clear the code and drive the car. If the misfire code changes to P0301 or P0303, then the coil you swapped is faulty and needs replacement.

  3. Check Fuel Injector:

    • Cause: A clogged or faulty fuel injector in cylinder 2 can prevent proper fuel delivery.
    • Action: This is harder to diagnose without specialized tools. You can try a fuel system cleaner, but if the problem persists after checking plugs and coils, a mechanic can test the injector's resistance and spray pattern.

  4. Compression Test:

    • Cause: Less common, but a mechanical issue like a bad valve, head gasket, or piston ring could cause a misfire.
    • Action: If all else fails, a compression test on cylinder 2 compared to the others can identify internal engine problems.

When to See a Shop:

  • If you're uncomfortable performing the diagnostics yourself.
  • If the issue persists after replacing spark plugs and swapping coils.
  • If the check engine light is flashing, which indicates a severe misfire that can damage the catalytic converter. Drive as little as possible in this scenario.
Menu

Help & account