P0300 on a 2019 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 2019 Ford F 150 Supercab

Ranked from 953 NHTSA owner complaints filed for this vehicle.

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1
Failing cam phasers / timing chain stretch (variable valve timing)
High severity
This is an extremely well-documented 3.5L EcoBoost defect (Ford TSB 19-2208/19-2365, CSP 21N03/21B10): the cam phaser locking pin fails to engage, producing a cold-start rattle, mistimed valve events, rough idle/sputtering, and in several complaints an explicitly logged engine misfire.
Reported in 21 NHTSA complaints
Parts:cam phaser timing chain kit
2
Chronic engine oil consumption starving cam phaser oil control
Medium severity
Multiple owners report significant oil consumption (up to a quart per 1,000 miles) with no visible leak; low oil pressure to the phaser oil control valves aggravates the cold-start rattle/misfire pattern on this engine.
Reported in 2 NHTSA complaints
3
Worn spark plugs
Low severity
Fouled or worn plugs are a standard misfire cause; note that in one case here plug replacement alone did not resolve the rattle/misfire, pointing to the cam phasers as the deeper issue.
Common cause
Parts:spark plug
4
Vacuum or intake leak
Medium severity
Unmetered air entering through a cracked hose or intake gasket leans out an individual cylinder enough to misfire under load.
Common cause
Parts:intake manifold gasket
5
Clogged or leaking fuel injector
Medium severity
A partially clogged or dribbling injector under- or over-fuels a cylinder, producing a repeatable misfire on that cylinder.
Common cause
Parts:fuel injector
6
Carbon-fouled intake valves (direct-injection buildup)
Low severity
GTDI engines like this 3.5L EcoBoost have no fuel washing the back of the intake valves, so carbon buildup over time can disrupt airflow/combustion on affected cylinders.
Common cause
7
Low compression from worn piston rings or valves
Medium severity
Mechanical wear reduces a cylinder's ability to build compression, causing a persistent misfire that ignition-parts replacement won't fix.
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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Matching symptoms

Car Runs Rough Flashing Check Engine Light