P0300
 

I recently got a code P0300, which is a "random or multiple misfire" code. I reset the computer after that, and it was fine, however, whenever I was passing and getting above 80 mph, the CEL would flash and then turn off.
My first instinct is to check the plugs, and see if that is the problem.
Haven't had time to do that yet, but does this sound familiar to anyone?

hi cole, welcome to the rX8 club. (I see you just recently registered)

Your first instinct was somewhat correct but spark plugs aren't the only thing that require inspection when dealing with a misfire on our cars. A common culprit is actually the ignition coils themselves. We have seen many cases of these coils failing pre-maturely and needing to be replaced.

do you have access to a multi-meter or to someone who has one and knows how to use it?
how many miles on the car?
I have the instructions on how to test each coil, let me go find the link for you.

don't panic, this is a common problem that can easily be fixed. If you are out of warranty, do NOT go to the dealership unless you like over paying them. ;) We have a few do it yourself guides on here that can walk you through the coil replacement (if necessary)

here is how to test the ignition coils: http://www.finishlineperformance.com...16-07-1793.pdf

Thanks! I didn't think it was a big deal, as it isn't really effecting my performance, I wouldn't even notice it if it didn't flash at me. lol And what do you mean by a multi-meter?
And I have a 3 month engine/drivetrain warranty so it should be covered.

Edit: it is an 04' auto with 107 miles on it.

Who is the warranty with....some third party place? Good luck with that.....maybe they will, but you are going to have to take it in with the CEL lit up and let them pull the code.

Anyway, the problem really is that let's say it is a coil going out. If it continues to get worse, eventually you will start having other issues such as too much unburnt fuel getting to the CAT and that can lead to CAT failure. That can be an expensive repair.

CAT = Catalytic converter.

Guys, don't go off on the whole "just replace the CAT with a midpipe" so soon on this guy, let's keep it to the coils/wires/plugs and get rid of the misfire!


What Jedi54 means by a multi-meter is a hand held volt/ohm meter that is usually capable of reading at least voltage and resistance.

The factory coils have been known to routinely Ohm within spec and STILL not work properly.

^........that is a very true statement.
Not sure how one would really, really confirm a bad coil(s) without swapping.

That's why most rely on mileage as the main determinant these days.

Yep, you know I'm on that wagon.
About 10-12k on plugs tops and 25-30k on coils. :p:


Which reminds me....I need to send you a PM after I do a wee more research. Don't want to waste your time.

Yeah, it is with a third party place. And idk if I can get it to light up again. lol
I wasn't sure how helpful they would be. I don't know if the code will be there if it just flashed and went off or if it would take it to stay on.

I believe it will be stored and if you go somewhere with the proper reader, they will see it.

Okay. I guess I will have my dad run it by the place I bought it from tomorrow. See what they will do for me.

If cat happened to fail, just replace the midpipe with RB supercat, problem solve~ :P

I would love to do that, but as I am paying for the car still, doing mods to my car isn't much of an option yet. lol

Hi guys, I'm having the same problem as well with cole33 and just recently replaced coils, plugs and wires and still doing the same rugged sound. I really gave up on DIY. Still getting P0300 code. I have 04 rx8 6MT with 105200km on it.

P0300 is Random misfire.

See the misfire thread in my signature at the bottom of my post. Misfires can be caused by many things.

God, I made a stupid thread back in the day and someone just had to bring it back up didn't they.....

It was on the cursed auto as well.

P0300
 

04 rx8 auto 6 month old maf gutted cat k and n box air filter new coils and plugs has 81000. After the car warms up it will stall at a stop then take 15 to 20 minutes to start back up took it to northtowne mazda and they're telling me it's the maf and they say I'm also getting trouble codes in the 100s and told me I have a sub striction in the cat that's getting in the exhaust flow and messing it up some how does this sound right because for some reason I don't think they're right?

I just realized I posted in the wrong thread. I'm having P0300, I've also noticed that my speedo is off by about 50% slower then what I'm actually doing. I did just put in an S2 tranny but does the speed come off the crank angle sensor or related to it? I know the crank angle is one the to-do list to check so I thought I might start there.

Cars a race car with no cat, new plugs, wires, and BHR coils, and stock intake with an aftermarket MAF.

It comes off the ABS sensors detecting wheel rpm