P0300 on a 2021 Ford F 150 Regular Cab
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 2021 Ford F 150 Regular Cab
Ranked from 941 NHTSA owner complaints filed for this vehicle.
- 1
Low-pressure fuel pump failure / fuel starvation (recall 25S75, NHTSA 25V455)
High severityA large recall population reports intermittent loss of fuel pressure causing stumbling, misfire codes, and stalling under acceleration; several owners note the truck signals cylinder misfire when the pump is actually starving the engine of fuel.
Reported in 9 NHTSA complaintsParts:fuel pump - 2
Excessive oil consumption fouling cylinders / valve damage (5.0L Coyote V8, Ford TSB 19-2365)
High severityOwners document the engine running critically low on oil with no warning, and one truck lost compression on cylinder 4 from piston/valve damage tied to this documented Coyote oil-consumption defect.
Reported in 5 NHTSA complaints - 3
Cracked or fouled spark plugs
Medium severityMultiple owners had misfires traced directly to cracked spark plugs on relatively low-mileage trucks, requiring full plug (and occasionally coil) replacement.
Reported in 3 NHTSA complaintsParts:spark plugs - 4
Cracked high-pressure fuel injector spraying fuel
High severityOne owner's fuel gauge dropped rapidly with a gasoline smell in the cabin; the dealer found a cracked high-pressure injector spraying raw fuel, which will cause misfire and a fire risk.
Reported in 1 NHTSA complaintParts:fuel injector - 5
Failing ignition coil
Medium severityCoil breakdown under load drops spark energy to one or more cylinders; one owner's misfire repair included replacing an ignition coil alongside the plugs.
Reported in 1 NHTSA complaintParts:ignition coil - 6
Vacuum leak
Medium severityUnmetered air entering after the MAF disrupts the air/fuel ratio enough to trigger a misfire, especially at idle; smoke-test the intake and PCV system.
Common cause - 7
Carbon-fouled intake valves
Low severityDirect-injection engines are prone to carbon buildup on the valve backs, disrupting airflow/fuel atomization into affected cylinders over time.
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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