P0300 Mazda -

Question

I had the code p0300 a few weeks ago. I replaced plugs at first the check enginme light went out. About a week later the check engine light came on again, I then replaced the ignition coils. The check engine light was still on. I then replaced the plug wires. The check engine light went out. I drove it for 4 days, then the check engine light came on again. I went back to have checked again this time it had error code 0421 (warm up catalyst) and the p0300 (random misfire).
My question is: could it be the fuel injectors that were causing the original problem or something else?

Answer 1

HI there,

I would be concerned with the pre cat. When you have misfires it can damage the converter. If it's plugged up a bit or plugging up, it can blow the exhaust back into the cylinders and cause a misfire. I think I would remove the converter and inspect the inside of it.