Could be a bad ignition coil each cylinder has its own
Auto Zone will check your computer codes for FREE...
301 means #1 cylinder has a misfire check plug or coil
po301 means cylinder 1 misfire
Type your answer here... An engine cylinder misfire has been detected in cylinder # 4 firewall 4 - 8 3 - 7 2 - 6 1 - 5 front of Ford Expedition
Trouble code P0301 means: Cylinder 1 Misfire Detected
Trouble code P0302 means: Cylinder 2 Misfire Detected
Trouble code P0301 means: Cylinder 1 Misfire Detected
P0303 : misfire cylinder #3
Cylinder #1 misfire.
Was an intake manifold gasket for me.
If the check engine light is flashing that means an engine cylinder misfire has been detected
In the past I have had an engine misfire due to a bad fuel injector. hope this helps.