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2022 Kia Sportage - Rough Idle and Misfire Codes P0301, P0303

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Chris P. · rep 0 · May 22, 3:05 AM · 1 replies · solved · Question

Vehicle: 2022 Kia Sportage LX

My 2022 Kia Sportage LX, with about 35,000 miles, suddenly started running really rough at idle and under light acceleration. The Check Engine Light came on, and when I scanned it, I got P0301 and P0303, indicating misfires in cylinders 1 and 3.

It feels like the engine is shaking, and there's a noticeable loss of power. I haven't done anything unusual recently, just regular maintenance. Could this be spark plugs already, or something more serious like an ignition coil? I'm hoping it's an easy fix.

Any thoughts on common causes for misfires in newer Sportages? What should I check first before heading to the dealership?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:05 AM

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ClearTheCode admin answer:

The P0301 and P0303 codes on your 2022 Kia Sportage indicate misfires specifically in cylinders 1 and 3. This is a common diagnostic scenario, and while it can be concerning, it's often a fixable issue. Misfires occur when one of the three elements for combustion (fuel, spark, or compression) is insufficient in a cylinder.

Here's a systematic approach to diagnose the problem:

  1. Ignition System (Most Common):
    • Ignition Coils: A failing ignition coil is a very frequent cause of misfires. Since you have misfires in two specific cylinders, you can try swapping the ignition coils from cylinder 1 and 3 with coils from known good cylinders (e.g., 2 and 4). If the misfire codes follow the coils (e.g., P0302 and P0304 appear), you've found your faulty coils.
    • Spark Plugs: While 35,000 miles is a bit early for spark plug failure in modern engines, a defective or fouled plug can cause a misfire. If swapping coils doesn't change the codes, consider inspecting or replacing the spark plugs in cylinders 1 and 3.
  2. Fuel Delivery System:
    • Fuel Injectors: A clogged or faulty fuel injector in cylinders 1 and 3 could be starving them of fuel. This is less common for two distinct cylinders simultaneously but possible. A fuel injector cleaner might help if it's a minor clog, but a professional might need to test injector pulse and spray pattern.
  3. Compression Issues (Less Likely for Two Distinct Cylinders Simultaneously):
    • Low compression in a cylinder due to valve issues, head gasket problems, or piston ring wear can cause misfires. This is usually a more serious mechanical issue and would require a compression test.

When to See a Shop:

  • If swapping ignition coils and inspecting spark plugs doesn't resolve the issue.
  • If you suspect a fuel injector problem or a compression issue, as these require specialized tools and expertise.
  • Continued driving with a persistent misfire can damage the catalytic converter due to unburnt fuel entering the exhaust. It's best to address this promptly.
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