P0302 & P0300 codes

Airondot · 11-24-2020, 09:09 PM

So there was no build up to the the cyl 2 misfire, it just started.

I have a 2009 base 370 sitting at ~70,000 miles with the only mod being an axle back exhaust.

I have up to this point replace the spark plugs and the ignition coil and no luck with the misfire. I've used a multimeter and probed the harness going into the coil and I'm reading ~12v, although this only proves that the harness isn't damaged. As well I've had a listen to the injector and its fine. I've read that it could be the camshaft position sensor so I took a resistance reading of both and on one I read 10.3MOhms, which seems a bit excessive, and the other one I was unable to get a reading (could be a problem with me, I didn't have a lot of time to check). Also as a side note, when I first crank my car I can smell exhaust fumes inside the cabin but this is more recent than the mis and could be unrelated. Also the only tools I really have access to is a code reader and a multimeter. Any advice would be appreciated .

SouthArk370Z · 11-24-2020, 11:20 PM

First thing I'd do is clean the MAFs. It's possible they're the problem and it's a quick/easy/cheap job. You might want to clean the TBs, also. Several threads on both jobs are on this site.

Airondot · 11-25-2020, 12:55 AM

Quote:

Originally Posted by SouthArk370Z

First thing I'd do is clean the MAFs. It's possible they're the problem and it's a quick/easy/cheap job. You might want to clean the TBs, also. Several threads on both jobs are on this site.

Sorry, forgot to mention the TBs are clean(First thing I did). Ill double check the MAFs but I did looked them over but didn't see anything but it wont hurt to clean them. In the event that cleaning doesn't work (probably not knowing my luck) anything else I should be on the lookout for? I've seen some instances of the ECM failing (same symptoms I have), how real of a possibility is that?

jchammond · 11-25-2020, 04:35 AM

You listed a PO300, which is a random misfire code...low fuel pressure can also set these codes.

SouthArk370Z · 11-25-2020, 06:50 AM

Quote:

Originally Posted by Airondot

Sorry, forgot to mention the TBs are clean(First thing I did). Ill double check the MAFs but I did looked them over but didn't see anything but it wont hurt to clean them. In the event that cleaning doesn't work (probably not knowing my luck) anything else I should be on the lookout for? I've seen some instances of the ECM failing (same symptoms I have), how real of a possibility is that?

ECMs seem to be very reliable but it's a possibility. Could be a dirty/bad injector. As per jchammond, it could be fuel pressure.

Wabbyy · 11-29-2020, 04:58 PM

Got the same misfire from cylinder 2 as well. In the process of installing new sparkplugs and hopefully that fix's it. If you find out what the problem is, please let me know. Good luck!

sportsman2003 · 11-29-2020, 06:44 PM

P0300 is nearly always a vacuum leak or air intake leak.

SonicVQ · 12-01-2020, 10:47 PM

When troubleshooting a misfire, the best starting point is to use an OBD scanner and look at your long and short term fuel trims.

Also, look at the mode $06 data, as it has misfire counters and you can get a sense if it is common to a cylinder bank. OBD Fusion has a very good diagnostic report that shows all this data.

You might want to also pull the plugs and see if they are all the same.

11-24-2020, 09:09 PM	#1 (permalink)
Airondot Base Member Join Date: Oct 2017 Location: San Diego Posts: 2 Drives: 09 370Z Rep Power: 8	P0302 & P0300 codes So there was no build up to the the cyl 2 misfire, it just started. I have a 2009 base 370 sitting at ~70,000 miles with the only mod being an axle back exhaust. I have up to this point replace the spark plugs and the ignition coil and no luck with the misfire. I've used a multimeter and probed the harness going into the coil and I'm reading ~12v, although this only proves that the harness isn't damaged. As well I've had a listen to the injector and its fine. I've read that it could be the camshaft position sensor so I took a resistance reading of both and on one I read 10.3MOhms, which seems a bit excessive, and the other one I was unable to get a reading (could be a problem with me, I didn't have a lot of time to check). Also as a side note, when I first crank my car I can smell exhaust fumes inside the cabin but this is more recent than the mis and could be unrelated. Also the only tools I really have access to is a code reader and a multimeter. Any advice would be appreciated .

11-24-2020, 11:20 PM	#2 (permalink)
SouthArk370Z Premium Member Join Date: Nov 2010 Location: South Arkansas Posts: 8,435 Drives: 2014 Challenger Rep Power: 324198	First thing I'd do is clean the MAFs. It's possible they're the problem and it's a quick/easy/cheap job. You might want to clean the TBs, also. Several threads on both jobs are on this site. __________________ Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

11-25-2020, 04:35 AM	#4 (permalink)
jchammond A True Z Fanatic Join Date: Nov 2014 Location: South Carolina Age: 58 Posts: 15,204 Drives: 13’ 370Z TS 7A/T Rep Power: 2684395	You listed a PO300, which is a random misfire code...low fuel pressure can also set these codes. __________________ MazWorx built long block \| FI-TT-100 Stage 2.75 \| IPT built 7A/T http://www.the370z.com/members-370z-...s-musings.html

11-29-2020, 04:58 PM	#6 (permalink)
Wabbyy Base Member Join Date: Aug 2016 Location: New Jersey Posts: 58 Drives: 2009 370z Rep Power: 9	Got the same misfire from cylinder 2 as well. In the process of installing new sparkplugs and hopefully that fix's it. If you find out what the problem is, please let me know. Good luck! __________________ Double Layer Tints (5% on top of 15%), Muffler/Resonator Delete, Z1 Long Tube Intakes, Z1 Aluminum Undershroud, H&R Lowering Springs

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11-29-2020, 06:44 PM	#7 (permalink)
sportsman2003 Base Member Join Date: Dec 2018 Location: In the moment Posts: 191 Drives: Sideways most times Rep Power: 11606	P0300 is nearly always a vacuum leak or air intake leak.

12-01-2020, 10:47 PM	#8 (permalink)
SonicVQ Base Member Join Date: Jan 2016 Location: Ontario Posts: 230 Drives: G37 Sport Rep Power: 6720	When troubleshooting a misfire, the best starting point is to use an OBD scanner and look at your long and short term fuel trims. Also, look at the mode $06 data, as it has misfire counters and you can get a sense if it is common to a cylinder bank. OBD Fusion has a very good diagnostic report that shows all this data. You might want to also pull the plugs and see if they are all the same.