P0301 and P0300 solution

[Tommy]

So, while I was trying to correct my loss of fuel in this thread https://mazdaspeeds.org/index.php?threads/fuel-pressure-drops-then-stalls.5606/
I replaced a number of parts related to fuel. Prior to all this, I have had the P0301 and P0300 codes comes up for 3 years. I had accepted that this is due to low compression in cylinder 1 or 2 (don't recall) but it is now cured. I can not be 100% certain but the fuel pressure relief valve, based on my searching, can cause this if it is failing to hold the proper amount of fuel pressure. Since replacing the valve, these codes have not come back and I have over 1k miles on it since I have been back on the road. Sure, it's also possible the in tank fuel pump filter could cause a drop as well but I believe it to be the relief valve. Just posting for the next guy searching google to see why his/her 200k+ Mazdaspeed is getting misfire codes.

 

[Ervechkin]

Following up to this thread since I started with Google first.. almost as bad as WebMD-ing my symptoms when I have a sniffle..

I've had my 2011 Speed3 for going on two years now. Since owning the car, I've had various CEL pop up, most of which have been fixed by replacing parts. As of late though, I've had some come up that I'm not sure how/where to begin to correct them

-I've had the P0172 (rich air/fuel ratio) code intermittently pop up, it was coming and going as it pleased, but as of late, it's stayed on. I was told that it shouldn't be of any concern.

-I swapped out the injectors back in April, cleaned/de-carboned the throttle body and intake manifold, and everything was fine for a bit.. then got a P0089 (fuel pressure regulator) code.

The past week or so, when I cold start the car in the morning, it will come on, sputter a bit, and then shut off. When I start it again right after, it comes on just fine. It doesn't do it all the time, but more often than I'd like. I have noticed that the car has been idling pretty erratically as well. I changed the oil over the weekend and cleaned the MAF sensor. Went to leave for work this morning and found that I now have a P0300 code.

I'm fairly new to the platform, so any suggestions would be greatly appreciated. It sounds like the FPRV is a good start, which I've got on order. Aside from that, any insight as to what could possibly be causing the other codes?

Tuned by Will at PD Tuning
70K miles
Corksport Exhaust
Ultimate Racing FMIC (replacing with Treadstone TR8 this weekend)
JBR Intake (replacing with JBR Tur-3.0 Wide Path Full Silicone Intake this weekend)
Replaced the HPFP internals with Corksport

 

[Scaytale]

Low fuel pressure can cause intermittent misfiring, P0300.
If it were P0301 through P0304 that would be something specific to the particular cyl.
So based only on what you have said so far, it seems you know you have a Fuel pressure issue, low fuel pressure, and that can cause p0300.
I suspect when you get your fuel pressure squared away your P0300 will go away.
Of course it is possible to get P0301 through P0304 with low fuel pressure, but much more likely to get P0300.
I hope that is helpful, and that your question was about the P0300.