Tracking down my asymptomatic P0301 still
 

Just getting all my thoughts written down somewhere, so this will probably turn into a ramble. Let me preface this by getting my dumb question out of the way, just in case. Rotors are numbered front to back just like every other engine in the world, right? I know I've done far worse.

Had a thread about this before and had to push off taking care of it because accelerated summer courses pretty much buried me for 12 weeks. Quick background is no problems, code pops up on start up and hangs around. It'd go away for a bit randomly them come back. Reset and did 20 brake stomp and didn't come back for a few hundred miles. Then came back on start up and stuck around since then. Still no symptoms at all. ESS clean as it can get. Plugs, wires, and coils were about 6k miles old according to the PO (he bought the car, did a full tune up, then had to sell since he had a surprise kid on the way after 2k miles on it himself). Anyways I went ahead and swapped out the plugs on rotor 1. No code for a day or so. Then when I was out running errands I started the car after running into the school store and it popped back on. That was yesterday. Moving up I plan on changing the coils unless someone has another idea. I can post up a picture of the old plugs if that'll help. Stuff in and around the engine block is still pretty new territory to me, so I'm not sure if I read them right.

On another note I picked up some Duplicolor custom wrap clear coat to use on the front of the car since the paint has been getting eaten up by a 50 mile round trip commute 3-5 days a week. Sprayed it to essentially make a clear coat car bra. 1 trip down and it's holding up good. Cool stuff and feels better than plastidip.

Yes, rotor 1 is front, rotor 2 is rear. P0301 in Mazda'd documentation isn't "#1", but "Front rotor misfire".

Misfire instantly on startup and always on the same rotor suggests to me that you might have a coolant seal leak in the front rotor that is causing firing problems until it's swept out of the chamber.

Might be some other causes, but that is the first thing that comes to mind.

Thanks. Definitely wouldn't have gone in that direction myself. Looking back I did have the low coolant light pop up for all of 10 seconds when I redlined it merging onto the high way a few weeks ago. 90 degrees at night after an hour of high way driving, then parked for 10 minutes and a bit of stop and go before that happened. Never occurred before or after so I was concerned but put it off. So if I remember correct, I can pick up UV dye and a black light to hunt it down if I don't see it with my own eyes. Then if I still can't find it might have an issue.

A simple test would be to let the car sit overnight, then in the morning, hold the gas pedal to the floor to fut off fuel, give the starter a quick bump to spin the engine a couple revolutions to 'throw around' any possible fluids sitting there without throwing it enough to sweep it all out, then pull the front rotor plugs and see if there is fresh coolant on them. If they are dry, then i'd discount this and go looking elsewhere.

Even better. Quick once over and my engine bay looks dry as can be. Haven't started it yet, so might as well muscle it onto some 2x4s and jack it up. Have to check it underneath thoroughly anyway.

One day I'll get a lopro jack or ramps. All my jeep stuff is too tall.

Edit: Probably also important to note that it's not flashing. Between that and all the posts saying how finicky the PCM can be is why I haven't really had a sense of urgency. Even though I probably should

Again just updating for my own records. Just since it was free, I decided to check if it was the cat. So, I went and drove the piss out of it for a good half hour and had a blast. Came back and it wasn't glowing so I shut it down, and turned in for the night. Next morning I started it up and no CEL. Drove a 400 mile round trip with no issues and the light still hasn't come back nearly a week later. Good stuff.