P0300 on a 2021 Ford F 150 Super 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 Super Cab

Ranked from 941 NHTSA owner complaints filed for this vehicle.

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1
Cracked or worn spark plugs
High severity
Multiple owners of this exact 5.0L Coyote V8 had misfires traced to cracked or worn spark plugs, including one where all six plugs were replaced and another where a #1/3/4/6 misfire was resolved by plug replacement.
Reported in 3 NHTSA complaints
Parts:spark plugs
2
Failing ignition coil(s)
Medium severity
One owner replaced an ignition coil alongside plugs for a sudden misfire, and another had all coils replaced during a misfire diagnosis, pointing to coil breakdown as a repeat contributor.
Reported in 2 NHTSA complaints
Parts:ignition coil
3
Cracked or leaking fuel injector
Medium severity
One owner's misfire diagnosis included replacing all injectors, and another had a high-pressure injector crack and spray fuel, both consistent with injector-caused misfire.
Reported in 2 NHTSA complaints
Parts:fuel injector
4
Low compression from valve or piston damage
High severity
One owner's mechanic found a damaged #4 piston top from a suspected valve failure with severe power loss — a mechanical compression-loss misfire.
Reported in 1 NHTSA complaint
5
Vacuum or intake air leak
Medium severity
An unmetered air leak leans out one or more cylinders, often producing a rough idle or intermittent misfire.
Common cause
6
Carbon-fouled intake valves
Low severity
Direct-injection engines like the Coyote V8 don't wash intake valves with fuel, letting carbon deposits build and disrupt airflow/combustion.
Common cause
7
EGR valve fault
Low severity
A stuck or leaking EGR valve dilutes the intake charge unpredictably and can trigger a misfire.
Common cause
Parts: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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Matching symptoms

Car Runs Rough Flashing Check Engine Light