P0300 on a 2013 Nissan Altima
P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.
Not your vehicle? See general P0300 info.
Most common causes on the 2013 Nissan Altima
Ranked from 2,304 NHTSA owner complaints filed for this vehicle.
- 1
Failed Catalytic Converter
High severityA melted or restricted catalytic converter creates excessive exhaust backpressure, causing the engine to misfire or stall. Look for a check engine light, lack of power, or melted internals upon inspection.
Reported in 3 NHTSA complaints - 2
Faulty Mass Airflow (MAF) Sensor
Medium severityA faulty MAF sensor can cause incorrect air/fuel mixture readings, leading to random misfires. Look for MAF sensor codes or check engine light illumination related to the MAF circuit.
Reported in 2 NHTSA complaints - 3
Leaking Valve Cover Gasket (Oil in Spark Plug Wells)
Medium severityOil leaking from the valve cover gasket into the spark plug tubes can short out the ignition coils, causing random misfires. Look for a burning oil smell and oil pooling around the spark plugs and coils.
Reported in 1 NHTSA complaint - 4
Faulty Ignition Coils
Medium severityWeak or failing ignition coils will not provide enough spark to ignite the air/fuel mixture, resulting in misfires. Often caused by age or oil contamination from a leaking valve cover gasket.
Reported in 1 NHTSA complaint - 5
Faulty Spark Plugs
Low severityWorn or fouled spark plugs fail to ignite the air/fuel mixture properly, leading to random misfires. Inspect plugs for wear, carbon buildup, or oil contamination.
Reported in 1 NHTSA complaint - 6
Vacuum Leak
Medium severityUnmetered air entering the intake manifold leans out the air/fuel mixture, causing random misfires. Listen for a hissing sound and check fuel trim data.
Common cause - 7
Low Fuel Pressure / Faulty Fuel Pump
Medium severityInadequate fuel pressure starves the engine of fuel, causing a lean condition and random misfires across multiple cylinders. Verify with a fuel pressure gauge.
Common cause - 8
Faulty Fuel Injectors
Medium severityClogged or failing fuel injectors can deliver an incorrect amount of fuel, causing misfires. Check injector resistance and perform a balance test.
Common cause
These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.
Common symptoms
- Flashing or steady check engine light
- Rough idle
- Shaking under acceleration
- Loss of power
- Fuel smell from exhaust
What to check before replacing parts
Scan for cylinder-specific misfire codes
Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.
Inspect the spark plugs and coils
Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.
Check fuel trims for a vacuum leak
Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.
Verify fuel pressure
Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.
Compression / leak-down test if ignition and fuel check out
Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.
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