Running lean in cold weather

[AlphaWolf1993]

I hate to keep posting but it's a tad abnormal and I want to see if I can fix this, will delete when solved.

So temp have dropped to about 50ish during the day but a bit colder at night. Only recently and at night, I've noticed my afr idle and fluctuate toward ~15.2, but during day it runs 14.7 idle and driving (although it fluctuates under load, it's not much). I assume the problem is just the colder air, being denser and running it lean, but it's a stock tune on a mostly stock motor (built head, stock cams and bottom). Can I fix this or is it normal?

 

[Nick_C78]

Stock motor(mostly) and stock tune? You are fine. The fluctuation is the ecu reading sensors and compensating. Our cars have fairly old technology and the sensors aren't as good as more modern cars. Just let it warm up fully before driving it and you'll be ok.

 

[AlphaWolf1993]

OK, yeah the only aftermarket parts are supertech valvetrain, but everything else is stock and a stock gsr map on s300. It's not drastic and I've come to always let it warm up, I just get finicky when it moves to 15.2ish without me understanding.

 

[Nick_C78]

A lot of things can change your AFR, especially if you have some sensors disabled with your s300.

 

[Muckman]

O2 feedback is most likely disabled running open loop causing the S300 to run strictly off the fuel map unable to compensate for changes.

 

[AlphaWolf1993]

I believe I'm running it closed loop, I can see it compensating on occasion (it will slowly dial in idle if throttle sticks) and I believe that's how I was told to set it. I do, however have a few sensors disabled, ones that caused CEL. The highest the afr is reading is 5.4 when it kind of scavenges(?) for a reading, such as under load or cruising speed where not accel/decel. The car has not been tuned properly but will be hopefully soon. As I said, when it's warm and even earlier today during the day, no issue, afr is always 14.7 or slightly rich under load and runs great. I just wanted to make sure it's a normal occurrence because ive never monitored afr before this build. Thanks a lot guys