I would start with a compression test to be sure the motor is good.
The most common issue for the 300 code is low fuel pressure. I would have the fuel pressure tested to be sure it is not a fuel pump.
A mass air flow sensor could also cause this but it would code if it was reading wrong values.
Crankcase Ventilation System Vacuum Leak
Diagnose Other DTCs First
Exhaust System Restricted
Powertrain Control Module (PCM) Grounds and Connections Loose or Corroded
Spark Plug Worn, Fouled, Cracked or Incorrectly Gapped
Vacuum Hoses and Seals Split, Restricted or Connected Incorrectly
Thursday, July 18th, 2019 AT 10:19 AM