P0300 on a 2011 Ford Fusion Hybrid
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 2011 Ford Fusion Hybrid
Ranked from 2,869 NHTSA owner complaints filed for this vehicle.
- 1
Worn or fouled spark plug
Medium severityAn owner's cylinder-4 misfire was traced by a shop to a cross-threaded/damaged spark plug.
Reported in 1 NHTSA complaintParts:spark plug - 2
Vacuum/intake hose leak
Medium severityThe same misfire complaint began as a vacuum hose leak on the engine, a documented direct trigger for random/cylinder-specific misfire.
Reported in 1 NHTSA complaint - 3
EGR valve malfunction
Medium severityThe owner's shop also linked recurring rough-idle-at-stop symptoms on this misfire case to an EGR malfunction.
Reported in 1 NHTSA complaintParts:EGR valve - 4
Low compression from significant internal engine damage
High severityOne owner's engine suddenly misfired and stalled, which the dealer attributed to a catastrophic internal engine failure - consistent with sudden multi-cylinder compression loss.
Reported in 1 NHTSA complaint - 5
Failing ignition coil
Medium severityA weak or cracked coil delivers inconsistent spark energy, a leading cause of misfire on this engine family.
Common causeParts:ignition coil - 6
Clogged or leaking fuel injector
Medium severityA partially clogged or dripping injector under- or over-fuels a cylinder, producing a misfire.
Common causeParts:fuel injector - 7
Carbon-fouled intake valves
Low severityCarbon buildup on the valves disrupts airflow/sealing into the cylinder and can trigger intermittent misfire.
Common cause
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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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