Engine Misfire. Help. Please
10-06-2023, 07:20 AM
#1
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Thread Starter
Engine Misfire. Help. Please
Hey guys, i have a 2003 Nissan 350z Touring, and just today I drove to school, and my car drove just fine, and then I left my college class about a hour and a half afterwards, and started my car, and it was running really funny, like pulsing kinda you know, almost like I had LS Chop kinda thing, and so I stopped and checked it out, and it smelled like it was running really rich too... but i checked the codes, and nothing yet, but then by the time I got to my house (about a 10 minute drive) The "Service Engine Soon" Light was flashing, and then I checked the codes, and I had a ton... I had a bank 1, AND bank 2 csps codes, and Knock Sensor, ASWELL as a "Random Engine Misfire" code, but it didnt tell me which cylinder... can I have some help maybe? Thanks!
10-06-2023, 12:21 PM
#2
The sensor codes kinda make this an odd one. First thing I personally would do is check fluids for a potential gasket failure, alright sounds unlikely. and I would also check I’ll spark plugs for fouling, oil, etc. I had a misfire a while back and it didn’t tell me which one, too. If you have access to a power balance test to determine which cylinder, highly suggest. That narrowed down to cylinder 6 for me. Apparently the crank positions are notorious for going out, I’m pretty sure they are cheap and with some determination you probably won’t have to disassemble too much of the engine, just the intake. My honest guess is that your knock sensor is probably fine, your csps sensors mightttt need replacing, but most likely something is hindering ignition. Ie: coils or spark plugs. Ps. When the cel is flashing it just means a serious misfire that could/will harm the cats. Like I said more than likely one cylinder just isn’t firing would could be for a couple reasons. Also the factory service manual offers a pretty good diagnosis for a P0300 code. Link: https://www.nicoclub.com/nissan-service-manuals#350Z
If I remember correctly it’s in “engine control system” page 360 ish.
good luck
If I remember correctly it’s in “engine control system” page 360 ish.
good luck
Last edited by Coopa; 10-06-2023 at 01:29 PM.
10-07-2023, 03:07 PM
#3
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Thread Starter
The sensor codes kinda make this an odd one. First thing I personally would do is check fluids for a potential gasket failure, alright sounds unlikely. and I would also check I’ll spark plugs for fouling, oil, etc. I had a misfire a while back and it didn’t tell me which one, too. If you have access to a power balance test to determine which cylinder, highly suggest. That narrowed down to cylinder 6 for me. Apparently the crank positions are notorious for going out, I’m pretty sure they are cheap and with some determination you probably won’t have to disassemble too much of the engine, just the intake. My honest guess is that your knock sensor is probably fine, your csps sensors mightttt need replacing, but most likely something is hindering ignition. Ie: coils or spark plugs. Ps. When the cel is flashing it just means a serious misfire that could/will harm the cats. Like I said more than likely one cylinder just isn’t firing would could be for a couple reasons. Also the factory service manual offers a pretty good diagnosis for a P0300 code. Link: https://www.nicoclub.com/nissan-service-manuals#350Z
If I remember correctly it’s in “engine control system” page 360 ish.
good luck
If I remember correctly it’s in “engine control system” page 360 ish.
good luck
10-07-2023, 03:33 PM
#4
First thing i would rule out is potential head gasket failure but like I said probably unlikely. Look in the coolant reservoir for bubbles or emulsified oil. Then I would pull out and inspect all spark plugs, look for black fouling, oil, etc. anything irregular. Idk about the high flow cats, that sounds right, are they old? Prob unlikely but could be clogged cats. Only way to do a power balance test is with a nice code reader. I believe nissan uses the consulate II on 350z. I brought mine to a shop and they did a power balance for me. You might be able to get in touch with a shop and they will hook you up. If you feel comfortable, could you upload a video of what the idle sounds like? With a small rev? It might help be able to tell if it’s one or multiple cylinders. Overall though, check spark plugs or better get, if they are getting old, replace them and might as well do ignition coils. But still inspect spark plugs. If that doesn’t fix it, I would suggest a replacement for the csps and maybe the knock sensor. I get you had the code before and it seemed fine, but it’s still not normal to have lol. P0300 code sucks man. If you really wanna do it the right way, go through the factory service manual. But if you don’t wanna follow it, I would start on what I mentioned. I just thought of this, did you get a tune after installing those high flow cats? Could cause an issue.
Last edited by Coopa; 10-07-2023 at 03:49 PM.
10-08-2023, 10:04 AM
#5
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Thread Starter
First thing i would rule out is potential head gasket failure but like I said probably unlikely. Look in the coolant reservoir for bubbles or emulsified oil. Then I would pull out and inspect all spark plugs, look for black fouling, oil, etc. anything irregular. Idk about the high flow cats, that sounds right, are they old? Prob unlikely but could be clogged cats. Only way to do a power balance test is with a nice code reader. I believe nissan uses the consulate II on 350z. I brought mine to a shop and they did a power balance for me. You might be able to get in touch with a shop and they will hook you up. If you feel comfortable, could you upload a video of what the idle sounds like? With a small rev? It might help be able to tell if it’s one or multiple cylinders. Overall though, check spark plugs or better get, if they are getting old, replace them and might as well do ignition coils. But still inspect spark plugs. If that doesn’t fix it, I would suggest a replacement for the csps and maybe the knock sensor. I get you had the code before and it seemed fine, but it’s still not normal to have lol. P0300 code sucks man. If you really wanna do it the right way, go through the factory service manual. But if you don’t wanna follow it, I would start on what I mentioned. I just thought of this, did you get a tune after installing those high flow cats? Could cause an issue.
10-08-2023, 10:53 AM
#6
Okay, got it, and i will work on contacting a few shops, and I didnt get a tune with the high flow cats, i bought the car with them, and a y-pipe, but its been running perfectly fine with them since i got the car in march, so i dont know about that... but ill keep you updated, ill work on a video once I get the intake manifold and lower/upper plenum back on
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10-16-2023, 08:47 AM
#9
New Member
I second the notion that it could be sensor related. I had two camshaft position sensors fail slowly over time and that would crop up with odd errors. The crank sensor could also be an issue. these are very cheap and fairly easy to replace.
another possibility is bad gas! that sounds like a cliche but it happens. do you have a full tank? definitely want to use premium in these cars for best results. bad gas is a thing. If you bought it at a cheap station it could have been at the bottom of the tank.
just one of many things to troubleshoot. If you've got a lot of fuel in the tank, then you could put in a couple bottles of octane booster and see if that helps.
ps. I got some similar errors to that in my Mustang quite a few years ago and thought it was bad gas, and the errors were nonsensical, but it turned out to be both O2 sensors pre-cat. they were totally clogged from a rich tune and that confused the engine.
another possibility is bad gas! that sounds like a cliche but it happens. do you have a full tank? definitely want to use premium in these cars for best results. bad gas is a thing. If you bought it at a cheap station it could have been at the bottom of the tank.
just one of many things to troubleshoot. If you've got a lot of fuel in the tank, then you could put in a couple bottles of octane booster and see if that helps.
ps. I got some similar errors to that in my Mustang quite a few years ago and thought it was bad gas, and the errors were nonsensical, but it turned out to be both O2 sensors pre-cat. they were totally clogged from a rich tune and that confused the engine.
Last edited by Aeneas137; 10-16-2023 at 08:56 AM.
10-26-2023, 08:11 PM
#10
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Thread Starter
10-27-2023, 03:50 AM
#11
Im pretty sure the compression is a pass. I forget the numbers off the top of my head. Bur holy **** dude, good idea including the live data. Your LTFT (Long term fuel trim) is at 25% on bank 1 which I’m sure is the side that has cylinder 1 so passenger side. Which means the ECM is seeing a lean condition in one of those cylinders. I’ve been told of a way that you get a can of starter fluid and just spray it in the area and if you see/hear RPMs rise, congrats you got a vacuum leak. That makes me think you got a vacuum leak. However that narrows you down to cylinder 1, 3 or 5. How my fried coil acted was different. It basically only misfires at NOT but yours could be different. OEM is $50 from Napa so I suggest a replacement and it could be as easy as that. It sounds like more than 1 cylinder misfiring. Im sure the test pipes make your readings different but your voltages on the o2 sensors are out of wack. If there is not vacuum leak, this is my next guess. The important one is sensor 1, aka upstream of catalytic converters. If you decide to change that, suggest rock auto. OEM is like $40. As for reference my bank 1 sensor 1 hangs out at .3 and my bank 2 sensor 1 hangs at .6
Best of luck.
Best of luck.
Last edited by Coopa; 10-27-2023 at 05:05 AM.
10-27-2023, 06:18 AM
#12
New Member
you haven't mentioned the throttle body yet. did you leave it attached to the plenum when you removed that? might want to check the TB gasket or o-ring. and the rubber grommet attached to the air tube. If that's not incredibly tight, even a tiny amount of air coming in will cause issues like this. I think you mentioned replacing the MAF sensor. but is the air tube at the MAF mount OEM size? And finally, this could also be a tune problem. I know that was mentioned before, but what I mean is, maybe someone tuned it and it needs to be returned to OEM.
10-27-2023, 08:27 AM
#13
New Member
Thread Starter
you haven't mentioned the throttle body yet. did you leave it attached to the plenum when you removed that? might want to check the TB gasket or o-ring. and the rubber grommet attached to the air tube. If that's not incredibly tight, even a tiny amount of air coming in will cause issues like this. I think you mentioned replacing the MAF sensor. but is the air tube at the MAF mount OEM size? And finally, this could also be a tune problem. I know that was mentioned before, but what I mean is, maybe someone tuned it and it needs to be returned to OEM.
10-27-2023, 11:25 AM
#14
New Member
oh, I'm sorry, got this thread mixed up with another one. so the MAF sensor and TB can very easily cause problems that you're having. there's a TB position sensor that could be faulty and the MAF could be faulty. unfortunately, on an older car, regardless of mileage, the only way to troubleshoot these issues is to replace parts. The good news is, when you replaced something, you've renewed the car so it's not a waste even if you haven't solved the problem.
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Tech Territory (10-29-2023)
10-29-2023, 04:23 PM
#15
Keep me updated man, I’m curious. Unfortunately issues like these suck. But at least you can narrow to 1, 3 or 5. Some sort of lean condition which is sending more fuel to those cylinders. Only a few reasons for that.
10-29-2023, 06:14 PM
#16
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Thread Starter
will do man, and for sure, so how can I test for a vacuum leak?? or find one i guess? I can slightly hear the hissing on the passenger side, but im not sure ive heard like maybe blow some cigar smoke into the brake booster hose?? and the smoke will come out of the place its leaking?? or do i just have to spray everywhere? and where should I even spray??
10-31-2023, 07:01 AM
#18
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Thread Starter
um... I was putting parts into it that needed to be fixed anyways...? both my csps were bad, so i replaced them, and my knock sensor was bad, so i replaced it! Spark plugs were a few hundred miles past due according to fsm, so i replaced them! I can hear the vacuum leak, so im going to blow some smoke into the intake, and that should make me find my vacuum leak
10-31-2023, 09:22 AM
#19
Yeah you could use smoke or like I said starter fluid (not the one to start fires obviously) and it be fine. Smoke would tell you exactly where it is to be honest so probably the better option. Like you said you hear the hissing so it’s probably a vacuum leak somewhere. My guess would be headers but who knows ! Good luck.
11-02-2023, 08:12 AM
#20
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Thread Starter
Yeah you could use smoke or like I said starter fluid (not the one to start fires obviously) and it be fine. Smoke would tell you exactly where it is to be honest so probably the better option. Like you said you hear the hissing so it’s probably a vacuum leak somewhere. My guess would be headers but who knows ! Good luck.