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Most single-cylinder misfires end at one ignition coil — the part that turns 12 volts into the 20,000-plus volt spark. The ignition coil 30520-RRA-007 for the Honda 2.0 L and 2.4 L four-cylinders is that fix at $52.68.

Diagnosis decides the part number, not the other way around. Work the sections in order and you buy once.

What a coil-on-plug coil actually does

Coil-on-plug means one small coil sits straight on top of each spark plug. Your engine has one coil per cylinder, and each fires thousands of sparks a minute.

The COP versus distributor guide shows what this layout replaced. Older engines shared one coil through a distributor.

Four ways a coil actually fails

A coil rarely dies from age alone. Each failure mode leaves a clue you can see before you spend money.

• Internal insulation breakdown — heat and vibration age the epoxy, the windings short, and the spark weakens. A worn spark plug gap speeds this up.
• Cracked housing or carbon tracking — a burnt line down the casing leaks the spark to ground. Once tracking starts, the coil never recovers.
• Corroded spring contact — moisture creeps past the boot and rusts the spring that touches the plug.
• Oil-soaked boot — a leaking valve cover gasket fills the plug well with oil and kills the coil.

Worn plugs sit behind most of these cases. The aftermarket versus OEM spark plug guide tells you when a plug is due.

Read the code before you order

A misfire code names the cylinder that failed to burn its fuel. The digits tell you where to look.

• P0300 — random or multiple misfires; suspect fuel or air first.
• P0301 to P0308 — cylinder 1 to 8 is misfiring; that cylinder's coil is the prime suspect.
• P0351 to P0358 — the coil circuit itself reports a fault; letter A to H maps to cylinder 1 to 8.

P0352 plus P0302 points hard at the cylinder 2 coil. A P0300 with no coil code often is not a coil at all — the Accord P0300 misfire guide covers those look-alikes.

Two tests settle the argument

The swap test is the honest verdict. Move the suspect coil to a healthy neighbor, clear the codes, and drive until the misfire returns.

1. If the code moves with the coil, the coil is condemned.
2. If the misfire stays on the same cylinder, check the plug, injector, and compression instead.

The meter check adds numbers. A healthy coil reads 0.4 to 2 ohms across the two low-voltage pins, and 6,000 to 10,000 ohms from a pin to the spring inside the boot. Many failing coils measure fine cold and quit hot, so the swap test outranks the meter.

The coil resistance test walkthrough shows the full meter routine step by step.

Match the number, not the shape

Coils that look identical can carry different primary resistance and dwell timing. Your ECU was calibrated to one specific coil, so fitment is electrical before it is mechanical.

• Honda K-series: one number covers the seat — 30520-RRA-007, sold in the aftermarket as UF311. The full cross list sits in the table below.
• Nissan MR20DE and QR25DE: every coil in this seat comes from the 22448 family. The four-coil set for the 2007-2014 X-Trail T31 and 2007-2013 Dualis J10 covers all cylinders for $125.32.
• Refuse shape-alike crosses: NGK U5055 and U5315 serve unrelated engines (the table below shows which). Neither belongs in a Honda or Nissan four-cylinder.

Coil materials and quality standards explains why two coils with the same number can still differ in life.

Coils, plugs, and sensors for these engines sit in the engines and engine parts collection. Harness repairs and coil connectors live in starters, alternators, ECUs and wiring.

Coils for the other platforms in this guide

One rule holds across every brand: match the number first, then buy the count your engine needs. These KOEEP listings follow it.

• Toyota: the 90919-02239 coil for the 1999-2008 Corolla and 2003-2008 Matrix at $46.69.
• Mitsubishi: the 1832A016 coil for the 2007-2016 Lancer and Outlander Sport at $46.69.
• Kia: the 27301-3E400 coil for the 2007-2011 Magentis, Optima, and Rondo at $42.94.
• Subaru: the UF668 four-pack for the 2010-2012 Legacy and Outback 2.5 L H4 at $53.89 — boxer engines cook boots, so buy the set.
• Ford V8: the DG508 coils and plugs 8-pack for the 4.6 L and 5.4 L F-150 and Lincoln V8 at $69.99, with the DG508 OBD-II DTC reference for the 1998-2008 trucks.
• Two wheels: the 21171-0021 coil set for the 2003-2022 Kawasaki Ninja ZX-6R at $88.62 follows the same rule.

Replacing a coil so the fix lasts

The job takes about ten minutes per cylinder once you hold the right part. Work the steps in order.

1. Pull the misfire code and note the cylinder number.
2. Run the swap test before you spend any money.
3. Inspect the boot and the tower for oil or carbon tracking.
4. Found oil in the well? Price the valve cover gasket into the same job.
5. Fit new plugs on a high-mileage engine — a worn gap overworks every new coil.
6. Seat the coil fully, torque the fastener, clear the codes, and drive one warm cycle.

Frequently asked questions