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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
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.
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.
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