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2019 HR-V Rough Idle & Reduced MPG - Spark Plugs?

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Paul Z. · rep 0 · May 22, 2:46 AM · 1 replies · solved · Question

Vehicle: 2019 Honda HR-V EX

Hello ClearTheCode community, I'm having some issues with my 2019 Honda HR-V EX. It has about 65,000 miles on it, and lately, I've noticed a rougher idle than usual, especially when stopped at a light. Also, my fuel economy seems to have taken a hit, which is frustrating with gas prices these days.

I'm wondering if it's time to replace the spark plugs. I haven't changed them since I bought the car new. Is 65k miles a typical interval for spark plug replacement on these HR-Vs? Could worn spark plugs be causing both the rough idle and the lower MPG?

Any insights or DIY tips for changing them would be super helpful!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:46 AM

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ClearTheCode admin answer:

Your symptoms of a rough idle and reduced fuel economy at 65,000 miles are very consistent with worn spark plugs. Honda typically recommends spark plug replacement for the HR-V around 60,000 to 100,000 miles, depending on the specific engine and plug type (e.g., iridium plugs have longer lifespans). At 65,000 miles, it's definitely a prime candidate for replacement.

Causes of Rough Idle & Reduced MPG:

  1. Worn Spark Plugs: Over time, the electrodes on spark plugs erode, increasing the gap and requiring more voltage to fire. This leads to weaker, inconsistent sparks, resulting in misfires, rough idle, and incomplete combustion, which wastes fuel.
  2. Ignition Coils: A failing ignition coil can also cause misfires, mimicking worn spark plug symptoms. It's often a good idea to inspect coils when changing plugs.
  3. Fuel System Issues: Clogged fuel injectors or a dirty fuel filter can also affect fuel delivery and cause rough running.
  4. Air Filter: A very dirty air filter restricts airflow, impacting the air-fuel mixture.
  5. Oxygen Sensors: Faulty oxygen sensors can send incorrect data to the engine computer, leading to an improper air-fuel ratio and reduced efficiency.

Steps for DIY Spark Plug Replacement:

  1. Gather Tools: You'll need a spark plug socket (usually 14mm or 16mm), a ratchet, extensions, and a torque wrench. Always use OEM or equivalent quality iridium spark plugs specified for your HR-V.
  2. Access Plugs: Locate the ignition coils on top of the engine. Disconnect the electrical connectors and remove the bolts holding the coils in place. Carefully pull out the coils.
  3. Remove Old Plugs: Use the spark plug socket and extension to carefully unscrew the old spark plugs. Inspect them for signs of wear, oil fouling, or unusual deposits.
  4. Install New Plugs: Hand-thread the new spark plugs into the cylinder head to avoid cross-threading. Once finger-tight, use a torque wrench to tighten them to the manufacturer's specified torque (crucial to prevent damage).
  5. Reinstall Coils: Reinstall the ignition coils and reconnect their electrical connectors.

When to See a Shop:

  • If you're uncomfortable performing the replacement yourself, or if you encounter any difficulties.
  • If, after replacing the spark plugs, the rough idle and poor MPG persist. This could indicate other issues like a failing ignition coil, fuel injector problems, or a vacuum leak.
  • If your 'Check Engine' light comes on and you get OBD codes such as P0301, P0302, P0303, P0304 (Cylinder Misfire Detected for specific cylinders), or P0420 (Catalyst System Efficiency Below Threshold), which can sometimes be a secondary effect of prolonged misfires.
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