Sr20det lean idle

[jmitchell26]

hey i know there is a million threads on stuff like this but i cant seem to figure out my issue

fresh build

94 180sx s13 sr20det blacktop pretty much stock fmic, exhuast, stock ecu

car starts and idles at 1500rpm 13-14 afr then after like 10 min idle will finally drop down to 900 and afr will go to 17-18
when cruising afrs fluctuate 15-17
WOT 11.8-12.3 afr
the odd time it'll idle 900 and 14 afr which is were id think it should be

new tps and is set
base timing is set
no vacuum leaks
new maf
new water temp sensor
new injectors
no exhaust leaks pre wideband
took iacv off today and cleaned it all out (resistance checks out 10 and 20 ohms)
walboro fuel pump (ordered a new one cuz i did buy it used)
aeromotive fpr 43psi at idle
bov is recirculating
vacuum is 19hg at idle
did a dreadful compression test to be sure and 140psi across the board

if anyone has any tips on what i should check pls help ive been at this for over 6 months and now the car is about to be insured so want it running mint

[!Zar!]

Try a new 02 sensor.

[jmitchell26]

i have ecu 63 (skinny o2) bought an ecu 62 from a friend, and ordered a fatty o2 to test that but i always thought o2s do nothing at idle? only for cruising cuz its narrow band or whatever

[encludemeout]

Had a very similar issue that Enthalpy talked me through a few weeks ago. I rewired my fuel pump to a dedicated 30amp relay. Car runs perfect now.

Edit to be a bit more helpful. I experienced the same lean idle and kicked myself for days trying to figure it out. Boost leak tests, swapping mafs, etc. I probed the fuel pump with a multi meter and it was only reading ~ 12 volts. I never checked again after adding the relay, but it fixed the lean idle and car idles perfectly stoich now at 14.7.

I did make one other change that Martin suggested — it did help my issue, but didn’t solve it. I removed the ground strap that was on my maf harness. When doing this, the car immediately went from around 18.5 at idle to 17. But ultimately, relay on the fuel pump fixed it.