P0300 on a 2013 Ford Fusion
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 Ford Fusion
Ranked from 1,948 NHTSA owner complaints filed for this vehicle.
- 1
Coolant Intrusion into Cylinders / Cracked Engine Block
High severityCoolant leaks into the cylinders (often cylinder 2, 3, or 4) causing misfires, white smoke from the exhaust, and loss of coolant without external leaks. This is a known issue on the 1.5L/1.6L EcoBoost engines.
Reported in 10 NHTSA complaints - 2
Blown Head Gasket / Warped Cylinder Head
High severityOverheating due to coolant loss leads to head gasket failure or warped cylinder heads, causing coolant to mix with oil or enter the combustion chamber, resulting in misfires.
Reported in 5 NHTSA complaints - 3
Purge Valve (EVAP) Failure
Medium severityA stuck open purge valve can allow excess fuel vapor into the intake, causing a rich condition, stalling, and misfires, especially after refueling.
Reported in 1 NHTSA complaint - 4
Faulty Spark Plugs
Low severityWorn or fouled spark plugs fail to ignite the air/fuel mixture properly, leading to random or multiple cylinder misfires.
Common cause - 5
Faulty Ignition Coils
Medium severityA failing ignition coil pack will not provide sufficient voltage to the spark plug, causing a misfire condition.
Common cause - 6
Vacuum Leaks
Medium severityUnmetered air entering the intake manifold leans out the air/fuel mixture, which can cause random misfires across multiple cylinders.
Common cause - 7
Low Fuel Pressure / Failing Fuel Pump
Medium severityInsufficient fuel delivery prevents proper combustion, leading to lean misfires.
Common cause - 8
Faulty Fuel Injectors
Medium severityClogged or failing fuel injectors may not spray the correct amount of fuel, causing a misfire in the affected cylinders.
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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