P0300 Mazda Protégé

I have the same problem(P0300), random misfire. I replaced coil,spark and wire set like you. Then after 80 miles, got engine on and stupid P0300 code again. Did you resolve this problem? Anyone out there know what else is causing this misfit again? What else is wrong. Car is 2001, protégé-EX.

I thought it was a faulty coil pack and/or plugs so I replaced again. While taking out the spark plugs, I noticed 2 of them had oil on them. At that point, vehicle wouldn't start, and when it did it was extremely rough. Turned out to be the valve cover gasket leaking oil onto the plugs. Inexpensive part, less than $40. But I had it professionally installed. Runs just fine now. Do you notice any oil on your plugs?

Thanks for your reply. I got the exact same issue as yours. There is some oil in the spark plugs and socket area. I did the following: 1) Replace oil gasket in engine cover. 2) Took spark plug out and use blow torch and burnt off oil in thread and spark plug tip. 3) Clean spark plug socket area with Q-tip/WD40. 4) Clean spark plug boot, and installed spark plugs back in. 5) Drove to AdvanceAutoParts and borrowed scan equipment and clear check engine light. 6) So far driving car for 200miles and no check engine light. Keeping finger cross , my car reach 100K miles. Thanks for all your input! It really helps in my debugging. Hopefully my fix will help someone else.

Good luck. I got 185,000 miles out of my '02 Protege. It's a great commuter car and served me well over the years with no significant issues. But decided to trade it in recently.