Hey guys,
First a big hello
I just got a 2006 Mazda mps 6. About two weeks ago
And today the engine light came on lucky the car came with reader so found the code po421 looked it up either cat,o2 sensor or spark plug.
I did notice last two days after a cold start been getting a little miss hard to notice but idles fine and goes away quick
Sso advice do I look at replacing coil and spark plugs first
On furthur research comes up saying 99% is the cat
Thanks any help appreciated