P0304 on Lincoln
Cylinder 4 Misfire Detected
P0304 on Lincoln vehicles indicates cylinder 4 misfire detected. Au7o has documented this code across 2 Lincoln models — most commonly on MKX, Navigator. This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression. Typical repair costs on Lincoln range from $400 to $8,000, depending on the specific model and root cause.
Common Causes of P0304
- •Worn or fouled spark plug in cylinder 4
- •Failed or weak ignition coil on cylinder 4
- •Faulty spark plug wire or boot (where applicable)
- •Clogged, stuck or leaking fuel injector for cylinder 4
- •Vacuum or intake air leak near that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Damaged wiring or connector at the coil or injector
P0304 on Lincoln by Model
Lincoln MKX(1 issue)
- 2.7L EcoBoost Excessive Oil Consumption from Faulty Valve Guides2016-2017
2016-2017 Lincoln MKX models with the 2.7L EcoBoost V6 (engines built roughly April 2016 to January 2017) can suffer excessive oil consumption caused by defective cylinder head valve guides that let oil seep into the combustion chamber and burn off. Owners report burning roughly a quart every 3,000 miles, often accompanied by rough idle, misfires, and blue/white exhaust smoke. Ford addressed this in Technical Service Bulletin 19-2243, whose official remedy is replacement of both left and right cylinder heads. Fouled spark plugs from oil contamination commonly trigger cylinder-specific misfire codes.
Lincoln Navigator(1 issue)
- Navigator 5.4L 3V Triton Spark Plug Breakage on Removal2005-2008
The 5.4L 3-valve Triton V8 in 2005-2008 Navigator (and shared F-150/Expedition) uses a two-piece spark plug (Motorcraft SP-515/SP-546) that frequently snaps off in the cylinder head during removal. The lower portion stays welded into the head by carbon, leaving the upper electrode in the socket. Common at 60,000-100,000 miles when the first plug change is attempted.
Looking for P0304 on a different make?
View P0304 across all makes →Frequently Asked Questions
What does P0304 mean on Lincoln?▼
P0304 stands for "Cylinder 4 Misfire Detected." This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression. On Lincoln specifically, this code is documented across 2 models.
What causes P0304 on Lincoln vehicles?▼
Common causes on Lincoln: Worn or fouled spark plug in cylinder 4, Failed or weak ignition coil on cylinder 4, Faulty spark plug wire or boot (where applicable), Clogged, stuck or leaking fuel injector for cylinder 4, Vacuum or intake air leak near that cylinder. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0304 on a Lincoln?▼
Repair costs on Lincoln range from $400 to $8,000, depending on the specific model and root cause.
Which Lincoln models have P0304 documented?▼
Au7o has documented P0304 on 2 Lincoln models: MKX, Navigator.