So ive been fighting an intermittent misfire for ever...
 

Original thread for those who wanna read a bunch lol - http://www.the370z.com/intake-exhaus...de-post-3.html

Long story short:

Primary symptoms - intermittent misfire and lack of power, major stumbling after a Hot Engine restarts.

Nissan says it was AF sensors - I finally got both upstream sensors changed about 2 weeks ago, and holy **** it seemed fixed and no more CEL!

2 days ago... CEL came on, and after a long hot drive...turned it off... restarted about 10 mins later and sure enough back to the same dreaded stumble symptom....

its pretty much doing the same **** now as before.

So my questions here is wtf.... Did the new sensors actually fix it or was I just fooled by it driving better then usual for a little bit lol ? Or Did one or both of the new sensors magically fail within 2 weeks

(They were unopened Denso 234-9036 I found on ebay) Here is the Amazon link for the sensors: https://www.amazon.com/Denso-234-903...r=8-2-fkmrnull


I Need like a badass Nissan Z Yoda to help me or something this is driving me insane.

It sounds like you need an oil cooler.

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Sounds like you could be getting high AIT’s, which are read from one or both of the MAF’s...unsure your cai setup/ but the heat soaking can cause this problem.
Also don’t forget a possible low fuel pressure issue can cause as well & most times don’t throw a cel about fuel system; just random cylinder misfire. :ugh2:

I have a stillen 25 row. Deff not the issue. My oil temps barely ever get over 200.

All my mods are in my sig...

yea I installed new Mafs a while ago and have basically ruled out it as a Maf Issue... that when i had it at nissan on Consult 3 for like a day. They said it was absolutely the AFsensors.

Engine is bone stock.

I have been on the fence about it being fuel related for a while... Nissan said fuel was fine but then agreed it might be bad? said it was consistent at like 35psi I think.

Sadly enough I put in new fuel basket last year to try and solve the issue, then had a minor accident literally 2 days later and the hat broke on it so I put the old one back in. Fml.

35 seems a bit low...not sure what spec chart is. But thinking 40-45’ish

You run a stock fuel pump & hat?

Yea its stock FUel system. THink the FSM says like 50 psi or something.

Those stock systems are expensive lol like 500 bucks rip...

Like idc if it fixes it it will be worth it, but like a this point Ive spent like at least 1000$ ******* with this issue... It sucks to just keep throwing random stock parts in my car.

I’m seeing 40psi at the minimum,,,yeah-you can drop a couple bucks on the CJM fuel return system with external fuel filter...but very well designed kit with billet hat.
+ can upgrade pump a tad

The oem setup design routes the outlet of fuel pump to a 180* hose & down through a paper filter built into the basket...using a venturi to pull fuel from other side of tank & then a single line to engine bay....could have a restriction causing lower fuel pressures & can lead to random cylinder misfire codes

Also may try to carry some of those gel frozen ice bags along & when car does it....turn off & wrap or overlay them on the MAF’s to reduce temperatures...see what happens there.

Also, when does stumble occur,,,at idle,normal acceleration,wot,etc...

This is what’s inside your lower fuel pump housing, a paper filter.
This one had just 25k miles on it.

Would love to do the CJ return... super sketched out on doing all the weird mods to the basket my self lol like im good at handy stuff, but thats kinda out of my typical realm. (good news Is I have 3 fuel baskets right now, one is in the car... one is the broken one, and I have a third basket from a cheap ebay buy, but it had a cut hose)

Anyways the stumble... So the issue is weird.

After a cold start id say about 50-70% of the time, i feel a loss of power When trying to WOT around 3000rpm at pretty much any gear, you can feel it rev slower then a usual Z maybe even stumble a bit. The other 50% of the time It may not do this it may seem OK sometimes.

The big stumble happens after any decent amount of drive time: 20mins or so and around 180-200 degrees on oil temp... if I park it, then try to restart it before it gets cooled off, it has massive boggin issues...burble...shudder....misfire... struggles to get to any amount of speed, almost stalls out.... THEN the more gas i give and and the more i keep driving it, it starts to clear up and becomes normal again back to the same behavior as cold start driving. At least until I park it again.

THe shitty thing is this can deff be AF sensors.. or Fuel...or who knows lol.

After I put the new sensors on it, it drove the best it has since before the problem started.

But again that only lasted like 2 weeks.

Definitely sounds like low fuel pressure/ sounds like it’s an old carbureted car trying to vapor lock.
You can pick one of these up cheap & extend the line,so you can view while driving...just keep outside of vehicle.