P0300 on a 2020 Ford Expedition

Most common causes on the 2020 Ford Expedition

Ranked from 379 NHTSA owner complaints filed for this vehicle.

1. 1

   Cam phaser / variable valve timing wear causing timing rattle and misfire

   High severity

   The 3.5L EcoBoost used in this Expedition is known for cam phaser wear that produces a rattle at cold start and can throw timing off enough to misfire; two owners independently reported this exact rattle-at-startup symptom diagnosed by a dealer as a defective cam phaser.

   Reported in 2 NHTSA complaints

   Parts:cam phasertiming chain
2. 2

   Clogged or failing fuel injector(s)

   Medium severity

   A partially clogged or electrically failing injector starves a cylinder of fuel; one owner explicitly reported misfires with a loss of all power on acceleration.

   Reported in 1 NHTSA complaint

   Parts:fuel injector
3. 3

   Timing chain guide/tensioner wear introducing metal debris and disrupting cam timing

   High severity

   One owner's vehicle was diagnosed with failed front cover seals and an oil leak containing metal shavings, consistent with internal timing component wear on this engine family that can upset valve timing and trigger a misfire.

   Reported in 1 NHTSA complaint

   Parts:timing chaintiming chain guide
4. 4

   Worn or fouled spark plugs

   Medium severity

   The most common cross-manufacturer cause of a random/multiple misfire code, especially as gap erosion progresses with mileage on this turbocharged direct-injection V6.

   Common cause

   Parts:spark plugs
5. 5

   Failing ignition coil(s)

   Medium severity

   A weakening coil-on-plug unit can misfire intermittently, often worse under load or when hot.

   Common cause

   Parts:ignition coil
6. 6

   Direct-injection intake valve carbon buildup

   Medium severity

   Because fuel is injected directly into the cylinder rather than over the intake valves, carbon deposits accumulate on the valves over time and can disrupt airflow enough to cause a misfire.

   Common cause
7. 7

   Vacuum or intake leak

   Medium severity

   Unmetered air entering after the MAF sensor leans out one or more cylinders enough to misfire under certain conditions.

   Common cause

   Parts:intake gasketvacuum hose
8. 8

   Low cylinder compression from worn piston rings or valves

   High severity

   Mechanical wear reduces a cylinder's ability to seal and fire consistently, producing a chronic misfire.

   Common cause

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