shouldn't this have thrown a red flag when the car was tuned with the uprev??
it did it even before the uprev tune.
the other thing i am wondering is if it is power related, like something to do with my battery or a corroded ground somewhere. what is weird is that it seems to do it more frequently within the first 15 min of the car running or in extreme cold.

 

I believe the MAF we have operates like a toaster they run a resistive wire in the air flow. 0-5v signal will depend on how much air cools the wire. When air flow increases/decreases the wire cools/heats voltage drops/increases due to resistance from the air temperature. Ohms law the rest voltage increase current drop etc. Anyway, colder air is dense and will create a bigger voltage drop and a current increase to try and heat that wire up. During that extreme cool down it is possible the MAF Maxes out the voltage as the current tries to heat that wire back up. That is why it does this when it is colder.

 

sounds good to me.
so how do i fix it? i can't be the only one with this issue on a 7th gen.

 

You need to get an appropriate MAF Calibrator or have your ECM's MAP adjusted to give the MAF more range. The MAF itself is fine you just need a tad bit more resistance added. Do you have a air plenum or spacers added to your vehicle? Usually adding those contributes to the cool air factor. You don't need to take anything off just would like to know what I'm working with.

The 370z ECM compensates the MAF with additional internal ECM resistance. So possibly you could use URD MAF calibrator if its the type of MAF I think it is. I would also check to see if you have any ground loops in your car. Sometimes when aftermarket audio systems are installed or wiring is added or modified you can get ground loop noise contributing to a wrong voltage reading.

Let me know if you have any aftermarket systems installed or air spacing of any kind. Maybe you can resolve this without spending any kind of money.

 

Oh and also I just wanted to know if you could possibly datalog one of these events? Any little bit would help.

 

Your Uprev tuner should be able to monitor the MAF. Set up an appointment with them again and let us know.
The throttle closing is the computers way of protecting itself.

Side note what year is your car? Also where and how much was your tune?

 

2012 maxima
takeda intake
throttle body spacer (not installed anymore), manifold spacer (still installed)
i also did throw in an alpine amp with sub.
i can monitor maf myself if needed and log it for you.
tune was done at performance motorsports here on long island. i believe cost for everything was around $500.

thank you!!

 

Any modifications will only make it worse at this point. Our MAF Maxes out pretty quick. They max out at around the 320 HP range if your not forced induced. I'm not going to get into sucking and blowing.

Your intake spacer will contribute to your vacuum CFM. Because our cars intake diameters are adjusted for for our stock intake manifold runners and throttle body space. Yes having those things definitely help increase hp but nobody has bothered to make a MAF calibrator for our vehicles. Nevermind...I take that back there is a MAF calibrator for our cars but nobody has mass marketed it yet. This just means that someone with tuning experience will need to purchase one and install it make base maps etc. UPRev should have found a way to at least skew the intake diameter size.

They make modified MAFs for 370z and the GTR but neglected to apply some of that science our way. Sure the Modified MAFs will fit our vehicles but they need the MAF Calibration to work.

You will need to data log CFM along with MAF Voltage if you could. I need RPM vs CFM and Load%. MAF Voltage isn't as important as CFM vs RPM and Load%. This will give us a general idea where your car hits the top. The MAF Calibrator I found is close to $600 for our application made by SplitSecond. I used a splitsecond enricher from them once to enrich the partial boost area.

Anyway, once I get done with my current projects I will see if I can't buy one of those split second MAF Calibrators and get a MAP out. I will be needing it soon.

 

thanks for the info. i might shoot an email over to uprev and see what they say about it also. i will try to get that data over to you also by logging a few runs.

 

Keep me posted on any information you come by.

 

Did you ever figure out what the problem was? My car started doing that yesterday and this morning it was fine. I had all the power in the world but coming home from work, as soon as I gave her gas, it dogged down as if it wasn't getting air flow or something

 

What conditions were you in? I can't sort out all the different MAF sensor part numbers. It seems Nissan has been using the same type of MAF since 2004 but diffent types of part numbers. Performance definitely varies between part numbers.

 

My car is completely stock except a k&n air filter. It's about 25 degrees out and I have gas. It's doing it again as we speak. Kind of annoying

 

mine continues to do it. im ready to get rid of the car.
its like it will go wide open throttle and rev up and then all of a sudden it closes throttle to like 50%. after a second or two it starts pulling again. there is no pattern or anything to when it wants to do it. it seems to do it more in cold though i think, although i am beginning to think it just does it all the time. its been back to tuner numerous time and it couldnt be reproduced, dealer checked out car and couldn't reproduce, they checked tranny, fluid, no codes, everything checks out good.
i even went as far as replacing throttle body, MAF, and a bunch of other parts to try and correct it. anyone else have any ideas???

 

Dang! If I had just 5 minutes with your car I could definitely help you! We talked about datalogging when it happens but it seems like that's not going to happen very easily. Can you measure your fuel pressure at idle and on acceleration?

https://www.dropbox.com/s/a1lk0ivkf1...46.57%20PM.png

One datalog run on this vehicle revealed the culprit. MAF and in other screen shots maxed out fuel delivery. Knock was also a factor as it cut throttle back.

 

where do you live?
the data logging i can do will only log one thing at a time i think. when i logged the throttle position i could see it go from 100% to like 48%. it would just drop off and then spike back to 100%.

i doubt it is fuel delivery in my case because it has on occasion done it at half throttle too.

 

I live in Texas have a small shop in San Angelo I'm still in the process of setting up shop and working the projects I have right now.

Funny thing about the MAF, O2, Knock, CAM, Crank sensors, and fuel delivery is that they are all tied together. The only way to diagnose the problem is to see all the sensors datalogged together. If you knock it will cut out timing, if the timing cut is severe enough it will feather the throttle to help bring the knock threshold back to what it wants. Fuel cut, bad gas, and slip all feel the same many times.

https://www.dropbox.com/s/zu02qlf2sj...58.21%20PM.png

This screen shot displays the ECM's final timing (yellow line) vs the Stock Timing (red line). Yellow line is the Altered timing the red line is the factory ECM's requested timing. I added timing to the stock timing curve but if you look at the red line it climbs and then levels out. Where the red line levels out is where the car hit max fuel pump capacity and Maxed out the stock MAF. The timing curve just leveled out instead of climbing and the g/s on the MAF stayed the same. The car still climbed in RPM but very slowly. Point being is that the Stock ECM pulled everything back to level output to fall within the sensors threshold. This is how all new ECM's react to sensor feedback.

 

i wonder if i try knocking the timing back a little bit. maybe with the cold weather and fuel blend for the winter it is knocking a little bit and that is causing the issue?

 

I just checked my plugs on my other vehicle and noticed that the plugs looked like trash! The winter fuel is terrible!

Knocking, detonation, spark knock, pinging, pre-ignition and pinking are all kind of mashed together at times. I'm assuming you mean your getting a spark knock. Spark knock often times does come from trashy fuel which does make your car cut back on timing. To combat bad fuel I go to places that have to fill their station tanks often. I also run alcohol injection on every vehicle I own. I haven't installed alcohol injection on my Maxima because I got the 120,000 mile warranty on the vehicle. This is my first extended warranty purchase on any vehicle. The others were either a 3 yr or 36,000 miles mile warranty. None of my vehicles have made it past 36,000 miles. My highest mileage vehicle right now only has 32,000 miles on it and is an 06 Scion TC. In 09 when the warranty expired 20,000 miles I stuffed a built engine in it and boosted it.

Anyway, I got a bit off course there... What I meant to tell you in my novel is that your probably right with the winter gas there. I'm sure if you ask around you will find that nobody likes winter fuel at all.