PO300 Fault Code on 2003 GMC Truck - Intermittent Engine Shake and Reset Issue
My 2003 GMC truck is showing a PO300 generic misfire code. The engine shakes slightly when the code appears, and the check engine light flashes. After one to two days, the code disappears and the engine runs smoothly again. I've already replaced the spark plugs and ignition wires with new ones, and the coils have been tested and are functioning properly. Despite these efforts, the issue persists intermittently. Any advice or troubleshooting steps would be greatly appreciated.
Make sure you're using AC Delco spark plugs. Consider adding a fuel system cleaner like Techron or Seafoam. Also, check your fuel pressure — intermittent misfires can sometimes stem from fuel delivery issues. Since the problem is sporadic, use an OBD2 scanner to capture freeze frame data or monitor live engine parameters such as fuel trim maps when the symptom occurs.