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.

I have also heard a few members speak of throttle body issues causing similar issues...but unsure all details.
Confirm all connections to them are clean & even put a touch of dialectical lube on connection.

I have deff considered it being some kind of vapor lock when it is the hot start part of the issue... I have even heard of fuel rail vapor locks before on these IIRC.... But that seems odd and if any case you think it would be a rare issue...

Ill take a look at that part right now.

Vapor lock doesnt explain the colder engine issues...but bad fuel flow can. Either way its a Lean condition for sure ether thats from not enough fuel from the basket or a bad sensor not letting the ecu know whats up... so frustrating.

Way Back when the issue first started I cleaned Mafs, new spark plugs, and took off and cleaned the TBs real good. All that seems fine.

How many miles on engine & did it sit through winter with tank of fuel?

I Deff might buy this right now just because its cool and handy regardless.

Also, is it throwing a cel?

55,xxx miles

Uhh I store it each winter in a garage with less then a quarter of a tank.

This issue has been going on for almost 2 years or so... prob not just bad fuel

If you get on their website; they actually have videos of installation instructions...fairly simple.
Just mount gauge in a place that you can view while driving,,,just not inside your car.

Not good on 10% ethanol fuel,,,always a full tank & some ethanol shield to prevent corrosion around pump etc..

here is a pic of Nissans take on it

And here is a pic from my original post of all the codes I found with a 5000$ scanner lol.

I’d stay away from dealership & find shop familiar with the VQ....fuel pressure is low & definitely will cause a random cylinder misfire.
I don’t have specs in front of me...but should maintain 40psi....I’m pretty sure & in some cases more.
Your oil temp is fine...mine ran 220-230 a lot & wouldn’t pull timing & derate unless it got past 240-250

If you phone & order this/ ask to speak with Jon P. (Their Tuner) & let him know your symptoms & what fuel pressure reading was at dealership.
He will be able to give you some helpful information on it :tup:

Yeah I wish I lived near some of the reputable Z shops lol. Guess Ill have to dig around a lot here in rural NE Ohio for someone knowledgeable in VQ to look at it.

Is there anything common that could just kill a new AF sensor? Bad luck obviously lol.

Wonder if there is any other issue thats the main culprit that kills upstream sensor?

Other then that I guess I could just attempt the CJ return or buy a Brand new basket... both are the same price baically, assuming my sensors are still good then fuel is the last thing i can think of...

And yea its not going back to nissan, i gave them their 1 shot at diagnosing it.

Leaded race fuel will kill them or poor quality fuels,,,unless you’re somehow getting coolant down your exhaust.

Also if your fuel injectors are clogged & not atomizing fuel properly- could be sending unburnt raw fuel down exhaust.

Pull this website up & watch videos.

Thats what I was thinking of too, but it just seems kinda unlikely... ive thought about replacing injectors and coils before... its so simple just air, fuel, spark.... but at the same time its like a needle in a haystack.

Oh thats a cool service...only $25!!!

Yep; this company is the real deal on injectors...also ensure you have no exhaust leaks around cats or anything & wiring to AFR sensors are in stock location.
May be a bit tricky to find, but you’ll get there.
Dealership only knows to hang parts.
You may ask on Forum of a good tuning shop for 370’s near where you live:ugh2:

This place is very good & in driving distance...you may want to see who the Pennsylvania guy’s use.

Well I deff might have some exhaust leaks now since the minor accident lol.

I plan on getting a new catback system asap... just wanted to get it running as good as stock when i bought it before I start doing any power mods... But at this point I might just go for the mods and uprev and see if that fixes the issue in the process Lmao. Lol prob a dumb idea but im at witt end with possible options for this fix.

CONTACT US
13100 Middletown Industrial Blvd.
Louisville, KY 40223


Lol I bought the car in Louisville, KY. Its about 8 hours from me. I might hit them up tho and at least ask them about it.

Also deff need to see whos close by in PA... im only an hour or two from Pittsburgh... There may be some VQ tuners in Cleveland Ohio as well, thats only an hour away ish...

The 2 most popular aftermarket softwares for tuning are Ecutek & UpRev...not gonna say one is better than other,,,the tuner himself makes a huge difference.
Here’s a map of different shops near you.

Didnt know Ecutek could tune the Vq.... might hit the Ecutek guys up that are in Cleveland.

I’m gonna relax a bit before kicking off my day,,,hopefully some of this information will help you along the way- as it may take a Performance shop to pinpoint exact problem with your Z & definitely afterwards a tune will boost performance over the oem...regardless of your amount of mods. :tiphat: