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jackal
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Technical Assistance Required.

Postby jackal » April 26th, 2018, 4:39 pm

I have a Nissan NT30.

Having an issue with the vehicle, from around 2000 rpm to around 3000 rpm have a slight "missing" sometimes, only under load. Not getting any problems at no load, this makes difficult to diagnose.

No issues popping up on the ECU.

Checked a lot of mechanic, no help.

Started looking at it myself and discovered a reading on A/F ALPHA-B1 giving a reading of 95 to over 4 billion.

My question, what/where is the A/F ALPHA-B1 sensor?

I have changed the O2 sensor, rechecked the MAF sensor and a host of other components, still have the same problem

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skylinechild
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Re: Technical Assistance Required.

Postby skylinechild » April 26th, 2018, 6:44 pm

jackal wrote:I have a Nissan NT30.

Having an issue with the vehicle, from around 2000 rpm to around 3000 rpm have a slight "missing" sometimes, only under load. Not getting any problems at no load, this makes difficult to diagnose.

No issues popping up on the ECU.

Checked a lot of mechanic, no help.

Started looking at it myself and discovered a reading on A/F ALPHA-B1 giving a reading of 95 to over 4 billion.

My question, what/where is the A/F ALPHA-B1 sensor?

I have changed the O2 sensor, rechecked the MAF sensor and a host of other components, still have the same problem


quick question thou... how were you able to read the A.F ALPHA B-1 readings from the ECU??
what scan tool did you use ???

from a little googling....

there is no A/F ALPHA -B1 Sensor on the car.

A/F stand for air fuel ratio the B1 stands for bank 1.
if it was a v6 or v8 engine you have have 2 banks ( rows of pistons)
from what i understand it is a short term fuel trim correction mechanism - STFT
not to be confused with a long term fuel trim.

from what i got on the internet searching how it supposed to work.

internet wrote: The alpha correction indicates that the car has decided that the stock fuel map is not producing the proper mixture via the feedback loop, and the car is compensating by adding 10% (in the case of alpha = 110% for example) to the stock fuel map at the particular running condition.

To put it another way, say you have a completely stock car that is running perfectly. The alpha value when cruising at a particular RPM should theoretically be 100%. This means that the stock fuel map is producing a perfect fuel mixture which needs no correction.

Now lets say that you've just added an intake and an exhaust. There will be more air than the car is used to seeing at a lower throttle position, and thus the ECU will find itself at a different part of the stock fuel map. However, it may find that the wrong mixture is coming through, and produce a correction for it. This is where the alpha value comes in. It will enrichen the mixture if it's above 100%, or lean it out if it's below 100%. If the computer finds that it's making the same correction over and over again, it will eventually change the stock fuel map and the alpha will return to 100% with the new fuel map in place (this is called the long term fuel trim).

For this system to work properly, you need all of your sensors to be in tip top shape. If you have a bad O2 sensor, or a bad MAF (for example), your alpha value will be wrong and the car will make improper corrections to the fuel map, which could result in running too rich or too lean.


based on the above info and what youre saying - get a proper parameter analysis done on the car and have you sensors checked / cleaned / replaced.

it could be as simple as a proper cleaning of the MAF and throttle body and a new air filter or a pair of new sensors

it could also be a air intake leak- bad gasket somewhere - dont rule it out - seem many ppl try to fix throttle body / idling issues by getting a f - used bamboo one - just to fix an idling issue.

if you also use a K&N rechargeable filter it could be a little oil has somehow gotten on the MAF sensor...who knows....

check tuner ryotech performance hes an ASE qualified tech and his scan tool can read the ECU stuff just as good as the nissan consult.

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jackal
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Re: Technical Assistance Required.

Postby jackal » April 27th, 2018, 7:33 am

Since no defects was popping up on the Scan tool, I started to look at the operating parameters.

That is where I picked up the deviation in the reading. I used a Launch Scan tool, CR129.

So the thing now is to find out what feeds into the A/F ratio for the ECU.

Where is Roytech, and do you have a contact number.

I live in the Rio Claro area, so getting to him will have to be a planned event.

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VexXx Dogg
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Re: Technical Assistance Required.

Postby VexXx Dogg » April 27th, 2018, 8:49 am

Just curious, did you change plugs recently?

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skylinechild
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Re: Technical Assistance Required.

Postby skylinechild » April 27th, 2018, 12:49 pm

jackal wrote:Since no defects was popping up on the Scan tool, I started to look at the operating parameters.

That is where I picked up the deviation in the reading. I used a Launch Scan tool, CR129.

So the thing now is to find out what feeds into the A/F ratio for the ECU.

Where is Roytech, and do you have a contact number.

I live in the Rio Claro area, so getting to him will have to be a planned event.



i know the brand of scan tool ( launch) and they are a good quality unit.

the A/F - air fuel ratio is determined by several factors

factors include but not limited to - engine speed
engine load, load of electrics -ie EPS lights etc etc)
RPM,
driver inputs -ie acceleration / deceleration
air density / intake air temp
and most importantly by the ecu Maps and the trim level of the map. etc

the ecu map can best be explained as this
imagine a graduated tachometer from say 1000 rpm to 8000 rpm each thousand we will call a reference point.
that gives us 8 reference points.

for every reference point, the ECU knows the engine is running faster and faster and it has in its programming how much fuel is needed for a certain amount of air in order to give a perfect fuel mixture

the fuel trim comes in when say when theres an abnormal condition - and the ECU has to deviate from its pre-programmed set of values - either to rich the mixture ( add fuel) or lean it out (reduce fuel)

theres two types of fuel trim - short term fuel trim and long term fuel trim.

the short term fuel trim would come in -lets say if you accelerate suddenly in order to overtake another car
ECU sees the rise in engine RPM and the throttle open up more - the ECU looks on the map for the corresponding RPM value- reads the amount of air coming into the engine - calculates and adds in fuel to compensate for the extra air and boom you get more power.


the long term fuel trim comes into effect when the ECU sees that it has to make the same adjustments constantly.
the ECU "learns" this "correction" and deviates from its pre programmed maps values and instead uses the learned map values.

this is best explained when say for example you have a car that has not been serviced for quite some time..
all sensors values would be slightly incorrect and sending incorrect data to the ECU which then (automatically) makes corrections (and saves it) based on incorrect values.

when the system is cleaned the ECU now receives correct data from clean sensors but it wont idle correctly as its now referring to its long term fuel trim map instead of the preset base map values ( that the car came with)
which is why you would have to do an ECU relearn on newer cars i would think.

seeing as how you only experience this issue when the engine is under load - it seems that the MAF may sending an incorrect value to the ECU. (bad MAF) ..or air is being added in somewhere thats not accounted for
( intake leak)

ryotech performance aka Ryan contact info
talk to him and go in and let him do a full parameter analysis on each sensor of the car and work from there.
>>> https://www.facebook.com/ryotechperformance440/

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