2005 Pontiac Grand Am SE 6 Cyl 3.4L
Changed out spark plugs, wires, IAC, catalytic converter, but rpm still fluctuates up and then down periodically
Check engine light! "Random Misfire"
Too many possible causes to really help you. I have lots of questions also. Would you say that when the engine runs that it is quiet? Do you hear any valvetrain noise / clicking that seems excessive? Was there other codes before the P0300 (random misfire) and if there were , what were the codes? I would replace the fuel pressure regulator as a strong possible cause here. They are well known for going bad on the 3.4 engine and the symptoms fit.