P0304 on Nissan: How to Diagnose & Fix
Cylinder 4 Misfire Detected
4 Nissan models · 6 documented issues · 1 critical · $50-$4,500 repair
P0304 on Nissan by model: symptoms, diagnosis and fix
The MR16DDT 1.6 DIG-T is a direct-injected engine, so fuel never washes the back of the intake valves. Combined with PCV oil vapor routed into the intake tract, hard carbon deposits accumulate on the valve stems and seats, typically becoming symptomatic between roughly 60,000 and 100,000 miles. Deposits disrupt airflow and prevent valves from sealing, producing cold-start rough idle, a shaking/shuddering idle that smooths out under load, hesitation and eventually stored misfire codes. Owners on Juke Forums repeatedly report chasing coils and injectors before finding the valves coked. The problem is aggravated by short-trip driving and extended oil-change intervals.
Common Symptoms
- Rough or shaking idle when cold
- Random and cylinder-specific misfires
- Hesitation or stumble on light throttle
- Reduced fuel economy
- Check engine light flashing under load
- Loss of power that improves briefly after an induction service
How to Fix
Confirm with a borescope through the intake port. Chemical induction cleaners and 'top-engine' foams give partial, temporary improvement; the durable fix is mechanical cleaning - walnut-shell blasting (or manual scrape/solvent soak) with the intake manifold removed - plus new intake manifold gaskets and fresh spark plugs. Replace a clogged PCV valve and clean the valve-cover oil separator/baffle at the same time or the deposits return quickly. Shortening oil-change intervals and using a quality low-SAPS oil slows re-accumulation.
Sources for this issue (2)
The four individual coil-on-plug ignition coils (Nissan 22448-1KC0A family) sit directly on top of the turbocharged MR16DDT and live in a hot, high-cylinder-pressure environment. The secondary windings break down with heat cycling, most commonly after 60,000-100,000 miles, and the failure is usually one coil at a time. Juke Forums threads document owners with a hard single-cylinder misfire code, a shaking engine and a flashing MIL, where swapping the suspect coil to another cylinder moves the code with it. Worn or incorrectly gapped plugs accelerate coil death because the coil has to fire a wider gap under boost.
Common Symptoms
- Flashing check engine light
- Engine shakes hard at idle
- Sudden loss of power / limp mode
- Sputtering or jerking on acceleration
- Fuel smell from exhaust
- Hard starting
How to Fix
Pull codes; if a specific cylinder is named, swap that coil with an adjacent cylinder and re-test - if the misfire follows the coil, the coil is bad. Replace with genuine Nissan/Hitachi coils rather than budget units, which have a poor track record on boosted Nissans. Always replace the spark plugs at the same time with the correct iridium plugs gapped to spec; a fouled or over-gapped plug is what killed the coil. Expect roughly $60-$110 per OEM coil plus plugs.
Sources for this issue (3)
The 6th generation Sentra with the 2.5L QR25DE engine is known for excessive oil consumption, often burning 1 quart every 1,000-2,000 miles. The issue is caused by worn piston rings and valve stem seals. The QR25DE engine design has tight piston ring tolerances that contribute to oil passing into the combustion chamber. Nissan performed an oil consumption test for warranty claims but many vehicles were out of warranty when the issue became severe.
Common Symptoms
- Oil level low between changes
- Blue smoke from exhaust on startup
- Oil consumption of 1 quart per 1,000-2,000 miles
- Fouled spark plugs
- Rough idle from oil-fouled plugs
How to Fix
Monitor oil level and top off between changes. For a permanent fix: piston ring replacement ($1,500-2,500) or engine rebuild ($2,500-4,000). Switching to a slightly thicker oil weight (5W-30 vs 5W-20) may reduce consumption slightly. Some owners have had success with high-mileage oil formulations that condition seals. Engine replacement with a used low-mileage unit is sometimes more cost-effective ($1,500-2,500 installed).
The GA16DE's valve cover gasket and its spark-plug-tube seals harden and leak with age and heat cycles. Oil weeps down the outside of the engine and, more importantly, pools inside the spark plug wells where it saturates the plug boots and can cause misfires and rough running. A partial gasket-only repair often doesn't hold once the tube seals have hardened. Nissan vehicles past ~75,000 miles are noted as substantially more likely to develop these cover/gasket leaks.
Common Symptoms
- Oil pooling in spark plug wells
- Oil leak/burning smell from top of engine
- Misfire or rough idle from oil-soaked plug boots
- Visible oil on the valve cover and exhaust side
How to Fix
Replace the valve cover gasket along with the spark-plug-tube seals (replace the complete valve cover assembly where the tube seals are not separately serviceable). Clean oil out of the plug wells and replace fouled plug boots/plugs.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- DNJ VC640G valve-cover gasket set with tube seals
Confirm engine and included grommets/tube seals; not 1995-1999.
- MAHLE/Victor Reinz VS50289 valve-cover gasket set
Confirm exact model year/engine and kit contents; not 1991-1994.
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Sources for this issue (2)
The VQ35DE engine in the 6th and 7th generation Maxima is prone to ignition coil failure. Coils typically fail one at a time, causing misfires on the affected cylinder. The rear bank (cylinders 1, 3, 5) coils fail more frequently due to heat soak from the firewall proximity. Coil failure is especially common after 60,000-80,000 miles and is one of the most reported Maxima issues.
Common Symptoms
- Engine misfire and rough idle
- Check engine light flashing
- Loss of power and hesitation
- Rough acceleration
- Increased fuel consumption
How to Fix
Replace failed ignition coil(s). It is recommended to replace all 6 coils at the same time along with spark plugs to prevent repeat failures. OEM Nissan coils cost $40-60 each; quality aftermarket (Hitachi, Denso) $25-40 each. Total parts for all 6: $150-360. Labor: $150-300 (rear bank is harder to access). DIY-friendly on front bank.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Nissan 2004-2008 ignition coil 22448-8J11C
Use only 2004-2008 Maxima and confirm VIN/supersession; sold individually.
- Genuine Nissan 2009-2014 ignition coil 22448-JA11C
Use only 2009-2014 Maxima and confirm VIN/supersession; sold individually.
- Genuine Nissan spark plug 22401-5M014 / NGK PLFR4A-11
Confirm VIN, production date, heat range and required quantity; do not substitute across every 2004-2008 car by year alone.
- Genuine Nissan spark plug 22401-ZE01B / NGK PLFR5A-11
Confirm VIN, production date, heat range and unusual package quantity before ordering; engine requires six plugs, not ten.
- Genuine Nissan 2009-2014 spark plug 22401-EW61C / NGK PLFR4A-11
Use only after confirming 2009-2014 Maxima, VIN, installed plug and seller package quantity; engine requires six.
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On many 2.5L QR25DE Altimas, the pre-catalytic converter material can deteriorate and be drawn back into the engine during valve overlap, scoring cylinder walls and accelerating oil consumption. Owners report needing to add oil frequently, loss of compression, rough running, and in severe cases complete engine failure. This issue is widely discussed in owner communities and tied to Nissan service information addressing catalyst and ECM updates on affected 2.5L cars.
Common Symptoms
- excessive oil consumption
- blue exhaust smoke
- check engine light
- rough idle
- loss of power
- engine knocking
- failed emissions test
How to Fix
Diagnosis usually includes checking oil consumption, compression, catalyst condition, and inspecting for catalyst substrate breakup. Repairs range from replacing the pre-cat/manifold and upstream O2 sensor to replacing the engine if cylinder damage is already present. Owners also commonly verify ECM calibration updates and monitor oil level closely after repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Evan Fischer REPN960339 integrated front manifold catalytic converter
Confirm emissions label, engine family and local law before purchase; gasket included.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipIf a 2.5L Altima is using oil, inspect the pre-cat before simply replacing valve cover gaskets or PCV parts; continued driving can turn a catalyst issue into a full engine replacement.
- TipPerform compression and leak-down testing before authorizing repairs, because many owners found the catalyst was only part of the problem once cylinder scoring had started.
Sources for this issue (3)
P0304 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0304 mean on a Nissan?
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 Nissan it is documented across 4 models: Juke, Sentra, Maxima, Altima.
What are the most common causes of P0304?
The most common causes of P0304 are: 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. The specific cause varies by vehicle.
How much does it cost to fix P0304 on a Nissan?
Published repair estimates on Nissan range from $50 to $4,500 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.