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.

:iagree:

I have not checked but does Nissan not have misfire data? If not that truly sucks because it is extremely helpful. Maybe Nissan is hyper sensitive to misfire, better than ford where you can damn near pull the plug and they still won’t throw any misfire code or information (or so I’m toldj.

I will steer clear of going to Nissan then! And when I clean the throttle body which part do I spray? And do I let it sit for a minute then wipe it clean?

There's more than one TB-cleaning DIY on this site. If you can't find it using the site's search, go to any big web search engine and add "site:the370z.com" to your search string.

I cleaned my throttle bodies tonight. They were dirty!!

I reset the ecu last Thursday. Engine light hasn’t came back on yet

Cleared the other code :) but p0300 came on today :( I truly don’t believe it’s misfiring. The performance is good

Code P0300
 

You probably wouldn’t feel slight intermittent misfires. You would need a real time scanner that can register individual misfire counts on each cylinder while driving, especially under load and WOP. It’s the only way to know what’s really going on.


Sent from my iPhone using Tapatalk

Gotta link to a scanner I can buy?

Any OBD2 scanner with realtime scanning feature should work. But you need to make sure that it is capable of providing/recording individual cylinder misfire information. I believe the scanner needs to have Mode 6 decoding capabilities, not sure.

I don't have a link to any particular scanner but you can Google it. I know the Autel brand of scanners have several with Mode 6 capabilities.

Hope this helps.

How often does this code pop up on your Z? A lot of us have this randomly but not very often

Google icarscan from launch. Gives full oem access to full vehicle, you’ll thank me later.

Sorry to reawake this thread
 

So Ive been getting this code most more often recently, Changed plugs bc im on 125k miles. Still getting code. I have berks hi flow cats, not sure if they need to be swapped out or what. Then also i saw that could be clutch/ flywheel, which i am also still on the factory clutch/ flywheel at 125k. So now i basically feel like im chasing an endless problem. On one single occasion i had a p0304 come up but only once did that happen. Also my start ups are very weak and stumble, I feel like this could be due to the cats being clogged but i wouldnt think they would be clogged already. Open to any advice.

hey guys

any updates on this? i recently starting throwing the same code. 2010 370z 70000 miles with berk hfc, stillen G3, and nismo exhaust with a Ecutek tune are the only mods currently. Clutch/flywheel replaced at approx 50,000 (CSC failed, tune and clutch/flywheel done at Specialty Z). It was running fine until about a week ago when it threw a code. idle is slightly rough but seems to run ok but i can tell its slightly off. check engine flashes and remains on and at one point would flash and disappear but now its just on all the time. changed the spark plugs with oem plugs, cleaned both TB's, didnt make a difference. My next moves are to clean the MAF's and re-inspect the plugs. Guy at the auto store said to check the gaps of the plugs and the coil connections that they may not be making good contact and recommended the contact gel they have, i wasnt sold on the 2 things he mentioned as im assuming the plugs would be pretty accurate from the dealer, possibly the coils but would be a hard to determine. Dont know where to go from there so im looking for any input?? thanks!!

Possible Fix for P0300
 

Recently had my engine rebuilt, the after install it started to throw the infamous P0300 code. Of course the thought was something was not put back together correctly within the engine. After checking several things...plugs, injectors, coil packs, cam sprockets, O2 sensors. I found the the fuel pump assembly had completely come apart in the tank. After replacing the fuel pump and clearing the code, the code is gone. Idles perfect and runs smooth without throwing the code.

Does this mean that all P0300 codes started off life as a specific code (P0301 etc...) that was later converted into P0300 when multiple coils were misfiring (assuming the P0300 is an actual misfire)?

Hi guys, I'm new here and I'm having same problem.
I bought the 2010 370z roadster last year, very low mileage with only 25,000 km (not miles).
It has same mod as well. Stillen cold air intake and exhaust system (love the sound).
I drove it for about 4k then I get the P0300 code one day randomly. I reset it and didn't get it for a week then it pops back. I talked to a mechanic and he said the same thing that it could be many reasons and I might want to start with the small ones first. He said it might be "bad" gas so I drive until the gas as low as it could then I fill up with a different station and reset the code. It went a full tank with no lights, so I thought I have figured it out. I refilled same station and a few days later same problem. I cleaned the TB and MAF but same thing after a week.
I saw somewhere that it could be vacuum leak and I tested that as well with no issues.

Someone in this thread mentioned it could be vibration. This could be the issue too, when idling I do noticed sometime the engine make a slight vibration that does feel like a misfire because when it does that vibration i noticed a little twitch in the RPM.

Any ideas guys? I am about to order spark plugs to change.

Sent from my SM-N950W using Tapatalk

Hi and welcome to the club :)) P0300 is most annoying code I`ve ever seen.
At first dont throw your money randomly to change the parts, buy cheap obd reader and try to shrink the area of search, could be very useful.
Compare maf voltages, injectors duty time, o2 sensors output for both banks 1 and 2.

What I did with no effect:
TB, MAF and MAP cleaning
New spark plugs
Intake vacuum leak test
Fuel injectors test

Than found that MAF voltage for the bank 1 and injectors duty time are higher, also primary O2 sensor readings is different from bank 2.

Finally:
Welding of all joints of exhaust manifolds and cats
new exhaust gaskets everywhere
new primary o2 sensor bank 1
and may be the real reason of a misfire - bank 1 maf tube was so overtighted by the clamp that it was actually squashed. So less maf tube diameter - wrong readings. Bought and installed new maf tubes.

Problem solved.

PS: check the oil pressure, probably its a broken gallery gasket.

Sounds like my issue. Any updates on fixing this?