P0300 on a 2019 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 2019 Ford F 150 Regular Cab

Ranked from 953 NHTSA owner complaints filed for this vehicle.

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1
Worn cam phasers / stretched timing chain (3.5L EcoBoost) causing incorrect valve timing
High severity
An overwhelming number of owners report the well-documented cold-start cam phaser rattle (Ford TSB 19-2365, campaigns 21B10/21N03); worn phasers and chain slack throw off valve timing and directly produce random/multiple misfires, often with rough idling or a stall.
Reported in 13 NHTSA complaints
Parts:cam phaser timing chain timing chain guides
2
Weak fuel pump / low fuel rail pressure
Medium severity
One owner reported a low fuel pressure warning with hard/extended cranking and a stall after startup; insufficient rail pressure under load leans out individual cylinders and triggers misfire.
Reported in 1 NHTSA complaint
Parts:fuel pump fuel filter
3
Worn or fouled spark plugs
Medium severity
Widened gaps or carbon fouling reduce spark energy, especially under boost on turbocharged engines; check gap and electrode condition against spec.
Common cause
Parts:spark plugs
4
Failing ignition coils
Medium severity
A weak or intermittently arcing coil produces a repeatable misfire on one or more cylinders, worse under load or when hot; swap-test between cylinders to confirm.
Common cause
Parts:ignition coil
5
Clogged or leaking fuel injectors
Medium severity
Deposits restrict spray pattern or an injector leaks down, causing a lean or flooded cylinder; injector balance/leak-down test isolates the culprit.
Common cause
Parts:fuel injector
6
Vacuum/intake leak
Medium severity
Unmetered air entering after the MAF leans out one or more cylinders; check intake boots, PCV lines, and brake booster hose for cracks.
Common cause
7
Carbon buildup on intake valves (direct-injection engine)
Low severity
GDI engines have no fuel washing the backs of the intake valves, so carbon accumulates over time and can disrupt airflow/atomization enough to cause a misfire on cold start.
Common cause
8
Low compression from worn rings or valve wear
High severity
A cylinder that can't build adequate compression will misfire regardless of ignition/fuel condition; a compression or leak-down test confirms this before replacing electrical parts.
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