Hi, I don't have a wideband but I was wondering when my car sits at idle when its warmed up, the air fuel(so it shows) jumps between lean and rich back in forth a a set speed? is my o2 bad, or is that normal, setup is a gen 2 jdm 3sgte with some bolt ons

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that is exactly how it should work.

k, butthe exhaust tone changes when it goes back and forth which it probally should, I just didn't think having it jump back and forth at idle was the way it should be, does anyone know y it does that?

Its called "closed loop". The gauge will jump back and forth during idle and cruising because the o2 sensor is correctly adjusting the a/f ratio to stay stoich during those times.

Your exhaust tone changes as the A:F changes?
Like a surging back and forth?

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The ECU adjusts the A:F ratio to feed the catalytic converter oxygen.

yeah i can heard the tone kinda when it changes back and forth, i have a full exhaust, ems powered downpipe 3inch, to a full 3inch all the way back, no cats or resnators, only a muffler at the end, so u are saying that between the time the air fuel is jumping its going stoich

also, i was wondering this, cause on my buddies s/c integra his air fuel is always rich at idle and doesn't move

sounds like your friend needs a new o2 sensor.

i noticed today, lets say i get back from driving and let it sit for 2 mins, the air fuel is still jumping back and forth, but give it like 5min at idle and the air fuel starts to straigten up and start to stay dead on in the middle, seem right?