Why Your Honda Fit Is Misfiring (And How to Stop It for Good)

How to Fix Ignition Coil Misfire

A misfire in your 2020 Honda Fit is a jarring experience, turning a normally smooth and reliable ride into a shaky, hesitant machine. While the immediate suspect is often the ignition coil itself, owner experiences reveal a more complex diagnostic puzzle where the root cause can be a fuel system issue, oil contamination, or even an electrical gremlin. The key is a methodical approach, as one owner learned: "That's why there was no rhyme or reason to the misfire codes. Bottom line, make sure you have a good OBD2 scanner and, just to be safe, always rescan to confirm codes are truly cleared before continuing diagnostics." — duragauge. This guide will walk you through the symptoms, diagnosis, and repair based on real-world fixes from other Fit owners.

Symptoms

When an ignition coil begins to fail or is affected by an underlying issue, your car will communicate its distress in unmistakable ways. The most common and noticeable symptom is the engine misfire itself. You’ll feel this as a distinct shuddering or jerking sensation, especially during acceleration. The engine may feel like it’s stumbling or "sputtering," losing power and rhythm. This "whipping motion" can be severe enough to shake the entire cabin and is often accompanied by a flashing check engine light, indicating a catalyst-damaging misfire is occurring.

Beyond the physical shake, starting problems are a major red flag. Your Fit may "struggle to start," cranking longer than usual before firing up, or it may start and then immediately run rough. In some cases described by owners, the misfires were so consistent across cylinders that they masked themselves as a different problem entirely. "So the problem was in computer I guess. The car runs so smooth now, I thought the clutch was in bad shape but it turns out it was the misfires from all cylinders that affected the overall driving experience." — honda28. This highlights how pervasive drivability issues—hesitation, poor fuel economy, and a general lack of smoothness—can all stem from a misfire condition.

Perhaps the most critical symptom to investigate visually is oil contamination. One owner’s detailed account is a textbook case: "oil in my ignition coil cylinder 3 got the code p0303 and replaced the ignition coil, then about 4000km got the code p0303 again but found oil in the cylinder, open the other cylinders but they were clean except for cylinder 3 which had blacked up." — nigthking1122. Finding oil in the spark plug tube, especially if it’s localized to one cylinder, points directly to a failure of the valve cover gasket or spark plug tube seals, not a faulty coil. This oil "blackens" the area, can foul spark plugs, and ultimately shorts out a new ignition coil, leading to a repeat failure.

Most Likely Cause

Based on the collective troubleshooting of owners, the single most likely cause of a persistent or recurring ignition coil misfire is oil contamination from a leaking valve cover gasket. While a coil can fail on its own due to age or heat, the data shows a pattern where replacing the coil is only a temporary fix if an underlying leak isn’t addressed. Oil seeping past worn seals in the valve cover and into the spark plug well creates a conductive path to ground. This allows the high voltage from the ignition coil to arc away from the spark plug, causing a weak spark or a complete misfire. The oil also degrades the rubber boot of the ignition coil and can foul the spark plug, compounding the problem. This explains why an owner would replace a coil, drive a few thousand miles, and have the same-cylinder misfire return.

How to Diagnose

Accurate diagnosis is everything. Throwing parts at the problem, as many have learned, is expensive and frustrating. Start with an OBD2 scanner. This is non-negotiable. Read the stored codes; a P0300 indicates a random misfire, while P0301, P0302, P0303, or P0304 will point you to the specific problematic cylinder (1 through 4). Clear the codes and take the car for a short drive to see if they return. As duragauge advised, always rescan to confirm.

Once you have a cylinder code, the next step is a visual and physical inspection. With the engine cool, remove the engine cover and locate the ignition coils on the valve cover. Carefully disconnect the electrical connector and remove the bolt holding the suspect coil in place. Gently pull the coil straight up and out of its tube. Immediately inspect for oil. Look inside the spark plug well and on the lower portion of the coil’s rubber boot. Is it wet, shiny, or blackened with residue? If it’s dry, the coil itself may be bad. If it’s oily, you’ve found your root cause.

For a dry well, you can perform a basic coil test by swapping the suspect coil with one from a known-good cylinder. Clear the codes again, drive, and rescan. If the misfire code "moves" to the cylinder where you placed the suspect coil, you’ve confirmed a bad coil. If the code stays on the original cylinder, the problem could be the spark plug, a fuel injector issue, or, as hinted in the data, a deeper fuel system or computer-related fault. "One things for sure, on your fit, fuel shouldn't be a problem lol. Is it a return based system or does it dead head? (I'm not sure on the L15's yet)" — Itfits ... Twss. This suggests that while less common, fuel delivery quirks specific to the engine design can contribute to misfire conditions and require more advanced diagnostics.

Step-by-Step Fix

If your diagnosis confirms oil in the spark plug tube, follow this repair procedure to fix the leak and replace any damaged components. This is a manageable DIY job with basic tools.

1. Gather Parts & Prep: Secure a new valve cover gasket set (which includes the spark plug tube seals) and a new ignition coil for the affected cylinder. It’s also highly recommended to replace the spark plug in that tube. Let the engine cool completely.
2. Disconnect the Battery: For safety, disconnect the negative terminal of the 12-volt battery.
3. Remove the Ignition Coils: Remove the engine cover. Disconnect the electrical connector from each coil by pressing the tab and pulling. Remove the 10mm bolt securing each coil, then gently twist and pull each coil straight up and out. Keep them organized.
4. Remove the Spark Plugs: Using a spark plug socket and a long extension, remove the spark plug from the oily cylinder. Inspect it for oil fouling.
5. Remove the Valve Cover: This step requires care. You’ll need to remove various brackets, hoses, and the PCV valve hose connected to the valve cover. Label or take pictures of connections. Unbolt the valve cover bolts in a criss-cross pattern, starting from the outside and working inwards. Lift the valve cover off.
6. Clean and Replace Gaskets: Thoroughly clean the mating surfaces of the cylinder head and the valve cover with a plastic scraper and brake cleaner. Remove all old gasket material. Install the new rubber spark plug tube seals into the valve cover. Place the new main valve cover gasket into its channel on the valve cover.
7. Reassemble: Carefully set the valve cover back onto the head. Hand-tighten the bolts in a criss-cross pattern to gradually compress the gasket. Torque the bolts to the manufacturer’s specification (typically around 7-8 ft-lbs in a specific sequence—consult a service manual). Reconnect all hoses and brackets.
8. Install New Components: Install the new spark plug into the affected cylinder, torquing it to spec (typically 13 ft-lbs). If the ignition coil boot was heavily contaminated with oil, replace the coil. Install all coils, secure them with the 10mm bolts, and reconnect the electrical connectors.
9. Reconnect Battery & Test: Reconnect the battery negative terminal. Start the engine. It may run rough for a moment as the computer relearns. Use your OBD2 scanner to clear any historical codes. Take the car for a test drive to ensure the misfire is resolved.

As one owner shared after their diagnostic journey: "Update / Resolution After a lot of troubleshooting, I finally got this resolved. The mechanical issue turned out to be just a single bad ignition coil." — duragauge. While their fix was the coil itself, the process of elimination they used is the same critical path you must follow.

Parts and Tools Needed

• Valve Cover Gasket Set: Includes the main gasket and four spark plug tube seals. Honda part number 12341-P5R-003 is a common reference, but always verify for your specific 2020 Fit L15 engine.
• Ignition Coil: It’s wise to replace the affected one. A common part number is 30520-R5Z-A01.
• Spark Plug: NGK or Denso Iridium plug, such as NGK ILZKR7B-11S (Denso SXU22HCR11S). Replace all four for optimal performance if near service interval.
• Basic Tool Set: Ratchet, 10mm socket (for coil bolts), spark plug socket (5/8" or 16mm), various extensions, torque wrench.
• Cleaning Supplies: Plastic gasket scraper, brake cleaner, shop towels.
• Diagnostic Tool: A reliable OBD2 scanner is essential.

Real Owner Costs

The cost to fix a misfire varies dramatically based on the root cause and who does the work.

• DIY - Coil-Only Fix: If it's simply one bad coil with no oil leak, your cost is just the part. As one owner noted, "At least I'm only about $55 into it so far with parts that didn't need replaced." — Scotsman. A single OEM-style coil can cost $50-$80.
• DIY - Valve Cover Gasket & Coil Fix: This is the most common permanent repair. A quality gasket set is $30-$50, plus a coil ($50-$80) and a spark plug ($10-$15). Your total DIY parts investment is under $150.
• Professional Repair - Coil Replacement: A shop will typically charge 0.5-1.0 hours of labor plus the part. Expect a bill between $200 and $350 for a single coil replacement.
• Professional Repair - Valve Cover Gasket Service: This is a more involved job. A shop may charge 2-3 hours of labor. With parts (gasket set, coil, spark plug, and possibly a full plug service), the total cost can range from $450 to $700 or more, depending on local labor rates.

These costs highlight the value of an accurate initial diagnosis. Paying a professional for a proper diagnosis, as one owner did, can save money in the long run: "But they recommended me a guy who worked with petrol engines for 25 years and has expensive diagnostic system/tools. Gave the car to him, couple hours later he called and he said it was fixed." — honda28.

Prevention

Preventing ignition coil misfires revolves around addressing the common causes before they strand you. The most effective step is to include a check of the spark plug wells during routine maintenance, such as when you replace spark plugs (recommended every 60,000-100,000 miles). When you remove the coils to change the plugs, inspect the tubes for any signs of oil. Catching a slow valve cover gasket leak early allows you to replace the gasket set before it ruins a coil or causes a misfire. Additionally, using high-quality ignition components and ensuring your engine isn’t experiencing problems that could lead to oil contamination (like excessive blow-by) will help maximize coil life. While not a common failure point on the 2020 Fit, being mindful of the fuel system's health, as alluded to by owners, means using good quality fuel and addressing any check engine lights related to fuel trim promptly.

What Owners Say

Real experiences from HONDA owners:

Success Stories

"But they recommended me a guy who worked with petrol engines for 25 years and has expensive diagnostic system/tools. Gave the car to him, couple hours later he called and he said it was fixed." — honda28 (source)

Owner Experiences

"oil in my ignition coil cylinder 3 got the code p0303 and replaced the ignition coil, then about 4000km got the code p0303 again but found oil in the cylinder, open the other cylinders but they were clean except for cylinder 3 which had blacked up. car is running fine it been 1000km, need help" — nigthking1122 (4,000 miles) (source)

"So the problem was in computer I guess. The car runs so smooth now, I thought the clutch was in bad shape but it turns out it was the misfires from all cylinders that affected the overall driving experience." — honda28 (source)

"One things for sure, on your fit, fuel shouldn't be a problem lol. Is it a return based system or does it dead head? (I'm not sure on the L15's yet) OMG LOL it's so funny I haven't seen that since my DSM days exactly what I had for about super AFC lol." — Itfits ... Twss (source)

Lessons Learned

⚠️ "I tried all that - twice .I still get the 5 blinks when ignition is ON. The only hope now is to do the 50-100 miles drive at 55-60mph (very late at night lol!)" — Zero2Hero (source)

Pro Tips from Owners

💡 "That's why there was no rhyme or reason to the misfire codes. Bottom line, make sure you have a good OBD2 scanner and, just to be safe, always rescan to confirm codes are truly cleared before continuing diagnostics." — duragauge (source)

💡 "But I think the main reason was when I was a kid I didn't realize every time you blow a head gasket you should resurface the head so I just kept slapping warped head on top of a new gasket over and over I was young and dumb lol." — Itfits ... Twss (source)

Real Repair Costs

"As I get an instant start when it does start, I don't think it's wiring. At least I'm only about $55 into it so far with parts that didn't need replaced." — Scotsman (source)

"Oh, i looked up and found a used head on ebay for you a while back, 200 bucks... not bad.. jesus im so sorry to hear all that. We need to start bothering honda to make this a f*ckin recall." — Domino Walker (source)

"At least I'm only about $55 into it so far with parts that didn't need replaced. I've ordered a WAI starter motor from Roc Auto- hopefully it's the fix." — Scotsman (source)

FAQ

Q: How long does it take to fix an ignition coil misfire? A: The time varies by cause. Swapping a single, easily accessible coil is a 15-30 minute DIY job. If you need to diagnose which coil is bad, add another 30 minutes. Repairing an oil leak by replacing the valve cover gasket is a more involved 2-4 hour project for a DIYer, as it requires careful disassembly and reassembly.

Q: Can I drive my Fit with a misfire? A: Do not drive with a flashing check engine light. A flashing light indicates a severe, active misfire that is dumping unburned fuel into the exhaust, which can quickly overheat and destroy the catalytic converter—a very expensive repair. A solid check engine light for a misfire means the fault is intermittent. While you might drive it cautiously a short distance to a shop or back home, it should be diagnosed immediately as performance and fuel economy will suffer.

Q: Is this a common issue on the 2020 Honda Fit? A: Based on owner discussions, ignition coil failures themselves are a typical wear item on many modern cars. The more notable pattern among Fit owners across generations is misfires caused by oil leakage from the valve cover into the spark plug tubes. This is a known failure point of the valve cover gasket seals over time and mileage, making it a common root cause of what appears to be a simple coil failure.

Q: DIY vs mechanic - what's recommended? A: If you are comfortable with basic tools and following mechanical steps, diagnosing a bad coil (via the swap test) and replacing it is very DIY-friendly. Replacing the valve cover gasket to fix an oil leak is a moderate DIY job; it requires patience, organization, and careful torqueing of bolts. If the diagnosis is unclear, or if you suspect a deeper fuel or computer issue like some owners described, investing in a professional diagnosis is wise. As the data shows, an expert with advanced tools can often pinpoint the problem quickly, saving you from buying unnecessary parts.

Q: Why did my misfire code come back after I replaced the coil? A: This is almost always due to an unresolved underlying issue. The most likely culprit, as detailed by an owner, is oil contamination: "replaced the ignition coil, then about 4000km got the code p0303 again but found oil in the cylinder." The oil shorted out the new coil. Other possibilities include a bad spark plug, a failing fuel injector on that cylinder, or a wiring harness problem to the coil.

Q: Could a misfire be caused by something other than the coil or a leak? A: Yes, but it's less common as the primary cause. Owners have mentioned the fuel system as a potential contributor, and in rare cases, software/computer glitches. One owner’s resolution involved the computer: "So the problem was in computer I guess." However, these are outliers. Always rule out the mechanical and electrical basics—coils, plugs, and oil leaks—first, as they account for the vast majority of misfires.