from a couple freescan logs i ran i think i may have a fuel issue.

At WOT the o2s are reading very lean and i get up to 5 degrees of knock...I just (yesterday) installed a new fuel filter and 02 sensors..btw it showed the same lean reading at WOT b4 these 2 were replaced...and after it still showed the same readings. So if it is not the fuel filter...are the only 2 possibilites the fuel pump cutting out at high volume or the injectors not firing(but that couldnt be b/c they fire good under normal throttle)? Also i checked for leaks in the headers and there seems to be none.

cruising at all speeds and under heavy throttle (say80%) the car runs great..the o2s are working properly and fuel is adequate..but at WOT when it gets up there it seems the fuel is inadequate...i am awaiting a fuel pressure tester in the mail to test...
I have the csv. excell file if anyone would like to look at it.

 

froma 67mph roll i punched it and here are the 02 readings

0.053 0.053
0.848 0.835
0.848 0.835
0.884 0.875
0.884 0.875
0.879 0.879
0.879 0.879
0.87 0.87
0.87 0.87
0.688 0.781
0.688 0.781
0.058 0.084
0.058 0.084
0.04 0.049
0.04 0.049
0.036 0.058
0.036 0.058
0.04 0.08
0.04 0.08
0.036 0.093
0.036 0.093
0.044 0.741
0.044 0.741
0.044 0.062
0.044 0.062
0.049 0.173
0.049 0.173
0.067 0.591
0.067 0.591
0.062 0.155
0.062 0.155
0.053 0.471
0.053 0.471
0.058 0.759
0.058 0.759
0.067 0.258
0.067 0.258
0.075 0.653
0.075 0.653
0.781 0.737

then it returns to normal (btween .1 ands .9)

Ion does my tunes and know most tuners lean it out up top but this LEAN? doubt it..plus the tune i run is the same tune 100s of LT1s run from him..any ideas guys?

 

If you want, send the .csv to me and I will look at it, but with just those numbers its nearly impossible to see what is happening.

 

Thanks uve got mail

 

Keep in mind that you're looking at output from a NARROW BAND oxygen sensor. What that means is that you may not be running "VERY" lean ... you may be running just a little lean. That's because of the narrow band of measurement. When the AFR moves away from 14.7, the sensor just says it's lean. You can't tell "how lean". It could be 14.9 or it could be 16.0! the scale is definately NOT linear (a wideband sensor is linear).

 

so besides doing a fuel pressure test at all rpms (even WOT) to make sure the fuel pressure dosent drop... what would be my most accurate test to find out the a/f ratio at WOT...im not familar with using a wideband or where to do it n such...would a dyno run show any results? or would that b dangerous b/c if i was indeed running lean i dont want to blow the motor

 

Yep. That's exactly what a dynotune is for ... to measure and adjust the AFR at WOT using a wideband O2. If you really want to know your AFR, you'll need to do that.

 

There is no reason for the tune to cause your car to run that lean unless the car was running lean to begin with. If you want to double check it though, upload the stock tune back on it and scan again.

 

thanks Ion i didnt think it was the tune..how do i flash the computer with the stock tune?

 

When I sent you the original instructions on how to upload the custom tune, one of the steps was to save your stock tune on the floppy. Use the name of stock tune you saved to program it using option #2 on the floppy.

 

so i dont need to do a read i just pick the 2nd option then when it says "enter source file name" i type in STOCK.BIN as it shows above that

it says available sourse files..STOCK.BIN and FLASH.BIN

 

Yep.

 

Stock O2 sensors stretch the truth a bit...lol

 

k thanks..im going to run the stock tune (as the fans wont come on) and run it at like 210 for my emmisions test

 

so the only way to truley see what the AFR is is to dynotune it?