P0300 on a 2019 Ford F 250 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 250 Regular Cab
Ranked from 1,151 NHTSA owner complaints filed for this vehicle.
- 1
Rocker arm / valvetrain failure
High severityAn owner reported a rocker-arm failure on the 6.7L diesel that directly 'caused engine misfire, loss of power, and unusual noise' — a documented failure mode on this engine.
Reported in 1 NHTSA complaintParts:rocker arm - 2
Fuel injector / high-pressure injection pump failure
High severityOne owner's truck was diagnosed with 'a defective fuel injector pump' leading to catastrophic engine wear and damage.
Reported in 1 NHTSA complaint - 3
Charge air cooler (CAC) hose / boost leak
Medium severityOne truck lost power with a 'Mass Air Flow Sensor' fault message and was found to have a failed CAC hose (replaced twice); a boost/charge-air leak upsets air metering and can produce rough-running/misfire symptoms.
Reported in 1 NHTSA complaintParts:charge air cooler hose - 4
EGR valve fault
Medium severityA dealer diagnosed a bad EGR valve after repeated 'lack of power' complaints on this truck.
Reported in 1 NHTSA complaintParts:EGR valve - 5
Rodent-damaged wiring harness
Medium severityOne truck's harness was found chewed by rodents, causing intermittent loss of power; damaged injector/ignition-circuit wiring is a known source of misfire on trucks that sit outdoors.
Reported in 1 NHTSA complaintParts:wiring harness - 6
Fuel injector wear or carbon fouling
Medium severityWorn or fouled injectors deliver an uneven spray pattern and can misfire under load.
Common causeParts:fuel injector - 7
Low compression from worn valvetrain or rings
Medium severityMechanical wear that reduces cylinder compression will produce a chronic misfire on that cylinder.
Common cause - 8
Glow plug failure (cold-start misfire)
Low severityOn a diesel, a failed glow plug is the equivalent of a bad spark plug and causes cold-start misfire on that cylinder.
Common causeParts:glow plug
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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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