Multiple Cylinder Misfire P0300
 

Hey guys i would love to have some help on figuring out what the issue is of why i keep getting the p0300 code. Iv changed the spark plugs, the coils have been checked that they are performing right. My horsepower and torque is alot less since iv been having this issue, and sometimes when gun it, it acts like its about to stall and then it picks up?? Any advice is appreciated... i had some ppl say it could be a sensor. Maybe O2 sensor. Thoughts?...:confused:

I had this issue - it was a failed O2 sensor (Driver side, Sensor 1 - which is the annoying upstream one), which was probably caused by a vacuum leak somewhere. It wasn't a consistent misfire, but after replacing the O2 sensor and checking all the lines/intakes/wherever there might be a leak, the misfire went away.

Welcome to the 370Z forums. I would definitely check for vacuum leaks. Also I would run a electrical check on all your 02 sensors. It is possible one or more of your 02 sensors failed. I would also check your catalytic converters while you are in there.

This code is difficult to chase, and I have seen all kinds of different solutions to it. I suspect it is vibration related.. I have even seen people have the dealer replace the flywheel to correct it. In my current Z I also see this code about 1-2 times year.. I just clear it and move on with my life.

Back in the day, I’d say distributor cap.
But could be anything from low fuel pressure & above spoken part’s.
Cam/crank sensor can cause,but would usually throw a code.
Some newer vehicles will not report low fuel pressure & this will cause a P0300.
Post what you find.

Post up your results and how you fixed this code.

Thank you Guys for your advice and help I will post up what I find!

Updates here OP? Just threw the code this morning (first truly cold start of season) but the car felt fine.

Should I clear it and see if it comes back before taking to my mechanic?

I just bought my first Z a few months ago and I'll be damned, the same code showed up.. The car runs fine - I can chirp the tires going into 3rd gear so I am assuming it is running about as good as it is supposed to.

I just cleared the code and moved on. If/when it comes back - I'll try to figure out what to do. Seems like as long as the car is running fine, it's not a big deal. But I am probably a little anal like the rest of you and do not want a check engine light....

The previous owner installed the Stillen cold air intakes.. I was wondering if I needed to run a "hotter" spark plug with the cold air intakes?

I'll follow this post and add any comments that might be helpful if I get mine figured out. Like the others have said, it's a pretty vague code to track down!!

The stock plugs will be fine, just get a tune and have your tuner turn it off. If you get an actual misfire is should give you a code for the cylinder it happened on

Thanks elhombre…

Wow I just threw this code today. The only mods I have are stillen G3 intakes and invidia catback exhaust. If it was vibration related I feel like it would've gone off a lot sooner. It has been slightly colder here also. I have no idea where to even start.

How many miles does everyone have?

I just turned 88K and the code was thrown on the first true cold day of fall here. Car didn't feel any different so I cleared it to see if it'd pop back up and it hasn't. Wonder if its a combination temperature/mileage thing.

Seems like other folks are right and its just a "what was that" catchall code.

Had high idle Friday night. Same Saturday morning and when I left work. Drove to auto zone to get codes read. When I went to leave and turned the car on, the high idling was gone. Will see what happens.

Update...
 

So I took my 2009 in to the dealer today and had them read the code and see what is causing it. I got a call late in the day and the tech said good news/bad news.. Bad news is that we can't figure out what's causing the code. Good news is your car is running great.

Here are the notes from what they did:
Could not find any current issue with car at this time. Could possibly be related to Timing Exhaust Retarders (what the hell is that?) but no issue was found with them. Pulled a code P0300. No drivability problem, monitor data with C111, timing ok, A/F sensor switching normal, mass air flow normal, reset ecm, test drove vehicle 3 miles.


The tech said to come back if it comes on again.. I mean, I took it to the dealer because I figured if anyone could figure this out, they should be able to... Needless to say, they didn't.

At least they were pretty good - didn't charge me the normal $98 diagnostic fee...


Just thought I would post this for thought. If it comes back and I ever get it figured out, I'll post again..