P0300 on a 2012 Ford F 150 Supercab
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 2012 Ford F 150 Supercab
Ranked from 1,717 NHTSA owner complaints filed for this vehicle.
- 1
Stretched timing chain and worn cam phasers (VCT solenoids)
High severityExtremely well-documented 3.5L EcoBoost failure: a start-up rattle from chain/phaser wear throws valve timing off enough to cause rough running and misfire-type codes; nine separate owners in this batch describe this exact rattle-and-timing-chain pattern.
Reported in 9 NHTSA complaints - 2
Internal engine damage (rod bearing/connecting rod failure)
High severityOne owner found a cracked block and a connecting rod that had impacted the block at cylinder #2, with a stored misfire code for that cylinder.
Reported in 1 NHTSA complaintParts:connecting rod bearing - 3
Worn or fouled spark plugs
Low severityCommon baseline cause of random misfire; check condition and gap.
Common causeParts:spark plugs - 4
Failing ignition coil(s)
Medium severityA weak coil drops spark on one cylinder; swap coils to confirm the misfire follows.
Common causeParts:ignition coil - 5
Clogged or leaking fuel injectors
Medium severityA restricted or dripping injector unbalances that cylinder's air/fuel ratio enough to misfire.
Common causeParts:fuel injector - 6
Vacuum or intake leak
Medium severityUnmetered air leans a cylinder enough to misfire, especially at idle.
Common cause - 7
Carbon-fouled intake valves
Low severityBuildup on the valves disrupts airflow/fuel atomization enough to cause a misfire.
Common cause - 8
EGR valve malfunction
Low severityA stuck-open EGR valve over-dilutes the charge at idle/light load.
Common causeParts:EGR valve
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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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