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2018 Discovery Sport HSE - Misfire on Cylinder 1 and Rough Idle (P0301)

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Brittany E. · rep 0 · May 22, 6:26 AM · 1 replies · solved · Question

Vehicle: 2018 Land Rover Discovery Sport HSE

Hey everyone,

I'm having an issue with my 2018 Land Rover Discovery Sport HSE. The check engine light came on yesterday, and the car has developed a noticeable rough idle, especially when cold. It feels a bit sluggish under acceleration too.

I hooked up my OBD-II scanner and pulled a P0301 code, which points to a misfire on cylinder 1. I haven't done any major maintenance recently, but I did fill up with gas a couple of days before this started. Could it be bad fuel, or something more serious?

Any ideas on what I should check first? I'm hoping it's something I can tackle myself before taking it to the dealership. Thanks in advance for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:26 AM

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ClearTheCode admin answer:

Hello John, a P0301 code indicates a misfire detected in cylinder 1. This is a common diagnostic trouble code, and while it can be frustrating, there are several common causes you can investigate.

Here are the steps to diagnose and potentially resolve the issue:

  1. Check Spark Plug and Ignition Coil: The most frequent culprits for a P0301 are a faulty spark plug or ignition coil in cylinder 1. You can try swapping the ignition coil from cylinder 1 with a coil from another cylinder (e.g., cylinder 2). If the misfire code then moves to cylinder 2 (P0302), you've identified a bad coil. If the code remains P0301, inspect the spark plug in cylinder 1 for wear, fouling, or damage. Replace if necessary.
  2. Inspect Fuel Injector: A clogged or failing fuel injector for cylinder 1 can also cause a misfire. You can test the injector's resistance with a multimeter or, similar to the coil, swap it with an injector from another cylinder to see if the misfire follows.
  3. Vacuum Leaks: Less common for a single-cylinder misfire, but a vacuum leak near cylinder 1 could lean out the air/fuel mixture enough to cause a misfire. Listen for hissing sounds or use a smoke machine to check for leaks.
  4. Compression Test: If the above steps don't resolve the issue, a compression test on cylinder 1 can reveal internal engine problems like a bad valve, head gasket, or piston ring, which would significantly impact combustion.

When to See a Shop:

If you've checked the spark plug, ignition coil, and fuel injector without success, or if you're uncomfortable performing these diagnostics, it's best to take your 2018 Land Rover Discovery Sport to a qualified mechanic. Persistent misfires can lead to catalytic converter damage over time, which is a much more expensive repair. A professional can perform advanced diagnostics, including fuel pressure tests, injector flow tests, and comprehensive compression/leak-down tests, to pinpoint the exact cause.

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