P0307 on Ford
Cylinder 7 Misfire Detected
P0307 on Ford vehicles indicates cylinder 7 misfire detected. Au7o has documented this code across 2 Ford models — most commonly on Crown Victoria, Expedition. P0307 means the engine computer detected a misfire on cylinder number 7 — that cylinder isn't burning its air/fuel mixture completely or at the right moment. The PCM senses this by watching for tiny slowdowns in crankshaft speed each time cylinder 7 should fire. A misfire wastes fuel, can dump raw fuel into the exhaust, and may damage the catalytic converter over time, which is why a persistent or severe misfire often makes the check engine light flash. You may feel rough idle, shaking, hesitation, or a loss of power. Typical repair costs on Ford range from $150 to $1,500, depending on the specific model and root cause.
Common Causes of P0307
- •Worn, fouled, or incorrectly gapped spark plug on cylinder 7
- •Failed ignition coil or coil-on-plug for cylinder 7
- •Faulty, clogged, or leaking fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Damaged spark plug wire or boot (on applicable engines)
- •Carbon buildup or sticking valve
P0307 on Ford by Model
Ford Crown Victoria(1 issue)
- 4.6L 2-Valve Spark Plug Ejection/Breakage1992-2011
The 4.6L 2-valve engine uses spark plugs that thread into aluminum heads with only a few threads of engagement. The plugs can eject from the head under load, stripping the threads. Later models (2004+) use a 2-piece plug design that can break during removal.
Ford Expedition(1 issue)
- 5.4L 2-Valve Spark Plug Blow-Out From Cylinder Head1997-2008
The 5.4L Triton 2-valve V8 in 1997-2008 Expeditions is notorious for spark plugs ejecting from the aluminum cylinder heads. The 2-valve heads have only 4 threads holding each spark plug, which is insufficient for the clamping force needed. Over time, the threads strip and the spark plug launches out of the head under combustion pressure, taking the ignition coil with it. This typically happens when spark plugs are removed and reinstalled, or spontaneously at high mileage.
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View P0307 across all makes →Frequently Asked Questions
What does P0307 mean on Ford?▼
P0307 stands for "Cylinder 7 Misfire Detected." P0307 means the engine computer detected a misfire on cylinder number 7 — that cylinder isn't burning its air/fuel mixture completely or at the right moment. The PCM senses this by watching for tiny slowdowns in crankshaft speed each time cylinder 7 should fire. A misfire wastes fuel, can dump raw fuel into the exhaust, and may damage the catalytic converter over time, which is why a persistent or severe misfire often makes the check engine light flash. You may feel rough idle, shaking, hesitation, or a loss of power. On Ford specifically, this code is documented across 2 models.
What causes P0307 on Ford vehicles?▼
Common causes on Ford: Worn, fouled, or incorrectly gapped spark plug on cylinder 7, Failed ignition coil or coil-on-plug for cylinder 7, Faulty, clogged, or leaking fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0307 on a Ford?▼
Repair costs on Ford range from $150 to $1,500, depending on the specific model and root cause.
Which Ford models have P0307 documented?▼
Au7o has documented P0307 on 2 Ford models: Crown Victoria, Expedition.