What's up guys, finally decided it would be best to post here and get some input from you guys.

My 2003 350Z's been out of commission for a couple weeks now. I turned it on to go to work and it was misfiring, really bad sounded like atleast 2 cylinders were not firing. I ran the code it threw and I got the infamous P0300 random misfire code.

First thing I did was check my crank/cam sensors and all seemed well. Checked my injectors, does cleared as well.
I did change my spark plugs AND the coil packs themselves.

I've checked and double checked all the wiring and they're all plugged in the correct order.

Went ahead and cleaned my MAF Sensor, checked plenum for leaks, all hoses, etc.

After all this, it's still misfiring.
I ran the check engine light again just for the heck of it and it gave me NATS Malfunction P1615.

Seems like I have a major headache forming, any help will be greatly appreciated!

 

Might be helpful to post how many miles are on your Z and what mods? What kind of spark plugs are you running?

 

Are you getting any codes?

 

100k miles. Car has JWT PopCharger, NWP 75mm throttle body, MD 5/16 Plenum Spacer, Megan Racing Test pipes, Megan Racing Y-Pipe and Megan Racing Single Exahust.

Had these on for a while now, don't think they're related to my problem.

spark plugs are the NGK ones.

 

First code was P0300 (Random misfire)
Second code was the NATS Malfunction one

 

^^ Thanks for the reply.

So, if I understand, your initial efforts got rid of the P0300 misfire code. But, now you are experiencing a NATS P1615 code. I’m not sure if the chronology here is correct.

I believe that a NATS Malfunction P1615 code can indicate a problem with the car’s ECM. Do you think it may be necessary to address an ECM problem, or is this problem unlikely?

 

Nope, still misfiring.

 

I've been getting the p0306 cylinder 6 and radom misfire almost every other time I drive the z. Clear it and it's ok the the day and will come back the next time I drive it. Changed plugs coils, and swapped #6 injector over to see if it followed, didn't.

101,xxx. TN kit, z1 angled spacer,
1 step colder ngks

Sorry if I am hijacking, didn't want to start another thread on misfire.

 

Subing for answer to problem...

 

Doesn't seem like anyone's going to be any help, I'll keep you guys posted if I get this issue solved.

Getting my car towed to a mechanic either tomorrow or Tuesday.

 

Misfires are a B to solve. I had one in my Frontier. It started in cylinder #3. I replaced that coil pack and all 4 plugs. Then once I fixed that, it went to cylinder #2. I replaced that coil pack and it never popped the code again...

 

misfires are difficult. Mine took me a couple of months to track down. For me it ended up being two coil boots and one coil pack. Boots sit in oil for years then degrade and misfire through the boot to the valve covers.

You got any oil down in the plug holes? If this problem persists and you are getting nowhere I would bet money on oil problems being a common misfire problem for everyone eventually on this car.

Your NATS code is something I am not able to figure in because it was not clear what the code is for.

I would also at first ignore your mods at first because of the comment that they had been installed and running fine for awhile. How long is awhile though?

Let us know what the dealer says...

Also, are you ever getting the flashing check engine light that is indicating the cats are overheating? Be careful that you don't burn up your cats during the process of tracking this problem down.
I had the flashing code a few times and pulled over immediately and shut the car off. The cats did smell hot but I never did damage them. Ironically the few times that it misfired hard enough to possibly damage the cats, shutting the car off and restarting it made the misfire go away.

 

Yah man, misfires are annoying.
I think it was bound to happen. I changed my valve covers because I had some oil in cylinder 2 and 4 I believe.
I've cleaned my spark plugs, cause they looked good, not burned or anything. I also change all 6 coil packs, just to eliminate all possible coil issues.

I've had all the mods on for almost a year now, so it can't be from those.

I did valve covers like a month before the misfiring started so idk if that could be the culprit.

I talked to a mechanic, he said Z's are known to have faulty cam/crank sensors so I went ahead and ordered both of those. Going to swap them as soon as they come in and cross my fingers and hope it fixes. If It doesn't, I'm just going to tow it to the shop and throw money at it.

The NATS code was P1615, from what I've read on it, it's something to do with the key and ECM, but I've never had any issues with it like other people have experienced.

 

And regarding cats, I have test pipes on the car so I don't think overheating cats would be an issue.

 

I have replaced both my camshaft and crankshaft sensors (all banks), but that wasn’t related to a misfiring problem in my case anyway. The symptoms when these sensors go bad are stalling at low speed and difficulty restarting the car.

 

Oh I see, thanks for the info!

I already ordered them, so might as well.

Update: I unplugged my MAF sensor while car was idling and nothing changed. Didn't stall out or anything. Car was still misfiring tho.

 

I think you are wise replacing these sensors since they typically start failing at 80k when they require replacement.

I know the frustrations of this type problem. I wish I could provide better help. The only thing I’ll mention is that a NATS Malfunction P1615 code can indicate a problem with the car’s ECM, which could manifest as random misfires.

My most sincere hope that you find the fix quickly.

 

Thanks for the help, I'll keep you updated when I get it fixed.

On the plus side, new wheels arrived and my Big Country Labs wing should be here soon!

 

Since you are randomly swapping in parts I don't know if you are interested in what I went through. It took me over 2 or 3 months and I have about 4 pages of handwritten notes on what I went through. But I just got on the internet every night when I got home from work and poured through misfire diagnosis tips and went through everything I could find, also went through the random misfire troubleshooting procedure in the service manual.
I'll admit I skipped a few of the items that were in my opinion either too much hassle to do in the middle of the winter or that I didn't feel in my gut would be likely to help and would have to come back to them if needed.
I also should mention that an OBDII scanner with live readings is needed for some of the tests you should perform or things you should watch. I patiently waited for the car to misfire, driving around with my scanner most of the time but I spent as little money as possible on the problem and ended up not buying anything I didn't need (to my recollection). Keep us updated and I'll be happy to try and look up more advice for you. There are also a few more threads on this subject but cannot remember if any of them solved their problem. Good luck, it's not an easy thing to track down!

 

What ended up being your problem?

And my cars comcarnsy misfiring, so I don't think it would be a good idea to take it out and drive it while logging.

My OBDII does have a live can feature but I've only used it on idle, is there any info I can give you from there to help me out?