Code P0300
 

I’ve done a lot of research on this forum about this misfire code and I am trying to track down the fix for it. I changed my spark plugs and the light ended up coming back on the other day. Now I’m thinking I need to change my coil packs? I’ve also read it could be fuel filter or my cats are clogged? I will replacing my cats with tomei test pipes soon anyways so maybe that’ll fix this issue! But I don’t really want to buy 6 new coil packs and replace them if I don’t have to. They’re priced at $88 a piece at Z1. Can I test my coil packs somehow to see if I have a bad coil? And how can I access my fuel filter and replace that?

A P0300 can be thrown for a LOT of reasons. Before you start swapping parts, I'd monitor some of the the sensors (eg, knock, O2, camshaft position, etc) that can cause a P0300 and verify they are working properly.

If the problem turns out to be coil-related, it's probably just one coil, not all six.

How can I figure out which coil is bad?

I had a new code pop up p1233. -_- this is so annoying now I have that code and p0300. I wonder if my stillen g3 intakes are causing any of this?

The FSM will have a procedure to check the coils.

Re P1223: Check your TB wiring/connectors.

P0300 means you have a random misfire not related to just one cylinder. If it was just one cylinder it would give you P0301 for cylinder one, P0302 for cylinder two and so on. So I need to ask, did you get a blinking check engine light while driving? If you did, do not drive the car. You may be causing damage to the cats and more if you continue driving it.

I had to learn the hard way on how to track down the cause of a P0300 code on my previous LS1 Vette. After changing everything there was to change, turned out to be valvetrain related (bad valve springs) and I traded it in at that point.

Like others have said, do not just throw parts at it. You may waste a lot of time and money when the culprit can be really simple.
Start with taking care of the new P1223 code. This has to do with your throttle position sensor. As suggested by others, make sure your connections are good. Once you're sure, I would try going back the stock intakes and clearing the codes. If they do not come back, you found your problem source.

When codes pop up, you always start with investigating recent changes and mods.

Excellent advice.

And don't make any more mods until you get this problem figured out. While it is possible that the cats are causing the problem, it is low on the list and there's a chance that changing, at this point, may make things worse.


Once again, a P0300 is a generic code that doesn't give any indication of the cause (a cylinder misfired for no apparent reason). You will have to track down the items that can cause the code and eliminate them one-by-one. The procedures Nissan uses are in the FSM (link in my sig).

OP, start by cleaning your MAFs and throttle bodies, including the connections. Double check that you've installed the intakes correctly. If the code comes back without a corresponding misfire code of an individual cylinder, then start replacing parts.

P0300 is a huge pain in the ***. It's way too general, so it does no good as a DTC. My tuner ended up turning it off since my flywheel rattled enough for the ECU to think I was misfiring.

I will check my TB tomorrow. I’ll probably even clean it

I’ve never had a blinking light! Hope to never have that. I’m gonna start with the throttle body and for p0300 I’ll have Nissan diagnose it and see if they can figure out where it’s coming from. And this p0300 code came on before I put the stillen intakes in. I reset the ecu and it wasn’t coming back on so I installed the G3s but over 500 miles later it did and this is when I changed my spark plugs and now it’s back on so idk what will fix it. So I hope Nissan figures it out!

Just want to echo what Chuck said - if you search P0300 on here, some of the solved cases involve a clutch/flywheel change, which suggests that this code can, in some cases, be vibration related and not necessarily ignition related as suggested by the code description. Anything that would create excess vibrations (as chuck said, TB/MAF cleaning and such) should be addressed. =)

When my car is stopped and idling I hear a rattle maybe that’s my flywheel rattling and could be causing the misfire?

Could be! The important thing to distinguish here is that, if this is the case, there is not actually any misfire. Just a vibration that the ECU suspects is misfire.

Yeah could be possible. I wish I could know for sure

This. If it were a legit misfire, it would tell you which cylinder was misfiring. You most likely don't actually have a misfire. Also, my experience was not with the stock setup, making that the cause of your problem unlikely.

Lastly, if you're not under warranty don't let Nissan near this one. It's opening up a bottomless pit of diagnostic fees.