RB20 running lean please help

[db0440]

Hey i am new here. i am driving a n 89 240sx with an RB20 basically stock all i have is a custom intake plenum, fmc, 3" exhaust. a few weeks ago my SAFC II went out. i have no idea why but the screen would not come on any more but the selector wheel would light up. the car would not start with the SAFC plugged in. this all happened while i was at work. i went into work everything was running great, and when i came out this happened. long story short i got a new SAFC II and my car is running really lean. with it unplugged and a jumper wire to connect the maf it is running like 14.7:1 at idle and when i tried to drive it it went down to like 18+ : 1. so i hooked up the new SAFC and to get it to run at a reasonable A/F i have to set it to like 35% correction and thats running like 13-15:1 A/F ratio at light throttle, and at idle it is 12.6:1 at like 12% correction. with the new safc hooked up and the correction where is is at the car runs pretty good. it has power and doesn't break up or anything. i have not tuned my hi throttle % yet so it is all at 0. but when i hit the gas (WOT) it at first it is ok and running 13:1 A/F ratio until about 2700 rpm then it hesitates and is running about 17:1 (still at 35% correction) A/F ratio, then at like 3k rpm it richens up to about 15:1 and has good power. this lean condition happened over nigh. before i went into work the car was running great and the most correction i was at was +18 (at idle running 12:1) and it was also in the negatives in boost. so i can't figure out what could happened over night that would cause it to run very lean. and also when i unplugged the SAFC and bridged the open pin for the maf it was running really lean. shouldn't the stock ECU run the A/F ratio rich? does anyone have any idea what could be making my car run lean? i was thinking possibly fuel pump and or filter? what do you guys think? thanks for your help, and sorry this is really long.

[Carryl]

what maf are you running ? What is the in/out calibration hte safc set to?

[DriftingisLame]

If you're not already running a larger fuel pump than stock, you should definately get a walbro, or 300zx or similar. However, the stock fuel pump is sufficient for low throttle driveability.

Is this AFR reading with a real wideband? How is the wideband mounted, and is there any possibility whatsoever of an exhaust leak before the sensor?

Change your fuel filter to a new 300zx one, you should have done this by now anyway, and it will only eliminate the possibility of a simple clogged filter into a complex driveability concern.

[Carl H]

sounds like the safc is setup wrong or you have a z32 maf on there.

[SullivanRacing06]

what maf do you have? tuning? injectors? what are your input output set at?

[Yellow4g63]

which wideband do you use?

[db0440]

hey thanks for your input so far. i will try and answer all the questions to the best of my abilities. i just bought the car like a month ago so i am still trying to figure out what all he has done and used.

the car is untuned right now, but i figured untuned it should still be running rich not lean under normal operating conditions. or atleast not need 35% correction to just get it lean enough to drive. they are stock injectors. it has i think a stock fuel pump (i will have to ask the previous owner) and i am pretty sure it has a 300zx fuel filter.

the car has a real wideband it is an aem uego. the maf is the stock maf. i have it set to 1 in 1 out i belive and the arrow is pointing to the top right corner.

tomorrow i am going to my friends shop and i will see if there might possibly be an exhast leak before the wideband.

[Carl H]

ugh...aem wideband.does the car run smooth at idle with no correction?also check the safc settings...they are different maf to maf so they must be set right to work correctly.if the car idles smoothly and runs smoothly with no correction i'd guess a failed sensor or bad leak in the exhaust before the sensor.