P0300 on a 2018 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 2018 Ford F 150 Regular Cab

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

Sort by:

1
Camshaft phaser failure (3.5L EcoBoost variable valve timing actuator)
High severity
A recurring, widely-documented failure on this engine family: worn/failed phasers throw off valve timing and cause rough running, a check-engine light, and a loud rattle on cold start; several complaints cite Ford TSBs/Customer Satisfaction Programs for this exact issue.
Reported in 3 NHTSA complaints
Parts:camshaft phaser timing chain
2
Low cylinder compression from worn/damaged valves or rings
High severity
One owner's cylinder-6 misfire persisted after spark plugs, coils, and injectors were all replaced; a compression test showed near-zero compression, and a separate complaint required valve replacement for a knocking engine — points to mechanical wear rather than an ignition/fuel part.
Reported in 2 NHTSA complaints
Parts:valves piston rings
3
Worn or carbon-fouled spark plugs
Medium severity
Plugs beyond service interval develop wide gaps or heavy carbon/oil fouling and misfire under load; pull and inspect gap and electrode wear on all cylinders.
Common cause
Parts:spark plugs
4
Failing ignition coil(s)
Medium severity
A cracked or heat-degraded coil produces a weak or intermittent spark on one cylinder; swapping the coil to a different cylinder and watching the misfire follow it confirms this.
Common cause
Parts:ignition coil
5
Clogged or leaking fuel injector(s)
Medium severity
A partially clogged or dribbling injector under- or over-fuels a cylinder; an injector balance/flow test isolates the bad one.
Common cause
Parts:fuel injector
6
Vacuum or intake air leak
Medium severity
Unmetered air entering after the airflow sensor leans one or more cylinders and destabilizes idle; smoke-test the intake tract, PCV, and brake booster hoses.
Common cause
7
Carbon-fouled intake valves
Low severity
Direct-injection engines build carbon deposits on the back of the intake valves that disrupt airflow and atomization, especially at idle/low RPM; confirmed with a borescope.
Common cause
8
Low cylinder compression (worn rings/valves)
High severity
Mechanical wear that no ignition or fuel part will fix; a compression or leak-down test confirms it and points to internal engine repair.
Common cause
9
EGR system fault
Medium severity
A stuck-open EGR valve or passage dumps excess exhaust gas into the intake at idle/cruise and destabilizes combustion.
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