P0300 on a 2018 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 2018 Ford F 150 Supercab

Ranked from 1,835 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Cam phaser / variable camshaft timing (VCT) failure
High severity
Extremely common on this 3.5L EcoBoost F-150 generation; worn phasers and a stretched timing chain throw off valve timing, causing cold-start rattle and rough running/misfire (TSB 21-2130, 23-2143, Customer Satisfaction Program 21N03).
Reported in 15 NHTSA complaints
Parts:variable camshaft timing (VCT) unit timing chain timing chain tensioner
2
Clogged or leaking fuel injector
High severity
One owner's misfiring cylinder was traced to fuel present in the cylinder with injectors replaced during diagnosis.
Reported in 1 NHTSA complaint
Parts:fuel injector
3
Low cylinder compression from internal engine damage
High severity
The same misfiring cylinder tested near 0% compression after all ignition/fuel parts were replaced, pointing to mechanical damage.
Reported in 1 NHTSA complaint
4
Worn spark plugs
Low severity
Standard high-mileage misfire cause; check gap/fouling first.
Common cause
Parts:spark plug
5
Failing ignition coil(s)
Medium severity
Weak or cracked coils are a routine misfire cause on this engine family.
Common cause
Parts:ignition coil
6
Vacuum leak
Medium severity
Unmetered air causes lean misfire, especially at idle.
Common cause
7
Carbon-fouled intake valves
Low severity
Direct-injection EcoBoost engines accumulate carbon on valves, disrupting airflow/combustion.
Common cause
8
EGR valve or passage fault
Low severity
A stuck or leaking EGR can cause rough idle and random misfire.
Common cause
Parts:EGR valve

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

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.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough Flashing Check Engine Light