Misfire and O2 sensor erratic voltage. It can be many things. Don't throw parts at the problem. Take it to a professional.
Trouble code P0301 means:Cylinder no.1 misfire detected
last one to touch it is at fault!! take it back & make them fix it.
Engine cylinders # 1 and # 4 are misfiring
Lean Condition caused by bad or restricted injectors
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means: Cylinder #1 misfire detected
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means:Cylinder 1 misfire detected
Trouble code P0301 means: Number 1 Cylinder Misfire Detected