P0304 on Infiniti: How to Diagnose & Fix
Cylinder 4 Misfire Detected
1 Infiniti model · 1 documented issue · $150-$900 repair
On Infiniti vehicles, P0304 (cylinder 4 misfire detected) is most often reported on the 2008-2013 Infiniti G37 as Ignition Coil Blistering and Failure Causing Cylinder Misfire (P0300-P0306) ($150-$900 repair). Replace the failed coil (and inspect all six for blistering); most shops replace all six with spark plugs once the first fails past 80k miles. Use OEM Hitachi coils—aftermarket units have a poor reputation on this engine. Each section below gives the symptoms, how to confirm the cause, the fix, parts and sources for that model.
Common causes of P0304 (all vehicles)
- 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 Infiniti by model: symptoms, diagnosis and fix
The Hitachi coil-on-plug units on the VQ37VHR are a recurring failure item on higher-mileage G37s. Heat and electrical stress cause the coil body to blister or bulge, producing a random or single-cylinder misfire, rough idle and flashing check-engine light. Infiniti's bulletin ITB11-017A (cited by owners and parts guides) tells technicians that a P0300-P0306 misfire with a blistered, deformed or melted coil outer surface indicates coil failure. On the VQ37 the rear bank coils are buried under the intake plenum, which drives labor cost.
Common Symptoms
- Rough idle or shaking at idle
- Flashing check engine light under load
- Misfire counts on one or more cylinders
- Hesitation and power loss
How to Fix
Replace the failed coil (and inspect all six for blistering); most shops replace all six with spark plugs once the first fails past 80k miles. Use OEM Hitachi coils—aftermarket units have a poor reputation on this engine. If coils fail repeatedly, check engine grounds. No recall.
Looking for P0304 on a different make?
View P0304 across all makes →Frequently asked questions
What does P0304 mean on a Infiniti?
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 Infiniti it is documented across 1 model: G37.
How do I diagnose P0304 on a Infiniti G37?
Replace the failed coil (and inspect all six for blistering); most shops replace all six with spark plugs once the first fails past 80k miles. Use OEM Hitachi coils—aftermarket units have a poor reputation on this engine. If coils fail repeatedly, check engine grounds. Published repair guidance and available estimates are in the G37 section on this page.
What causes P0304 on Infiniti vehicles?
Documented causes on Infiniti: Ignition Coil Blistering and Failure Causing Cylinder Misfire (P0300-P0306). Generic 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.
How much does it cost to fix P0304 on a Infiniti?
Published repair estimates on Infiniti range from $150 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.