I'm just curious what your AFR is at idle? On my OBDI '97 WS6 with headers (single cat MAC's), my O2's are very slugish at idle (maybe move 10mV). My AFR at idle is a pretty stable 12.6:1 (under closed loop conditions, car warmed up after driving around). As soon as I am off idle and under cruise conditions, my O2's are very active and my AFR becomes 14.5 to 15.0:1, averaging 14.7:1. AFR is pretty much fixed at 12.7:1 under WOT (I'm a little lean here yet, shooting for 12:1, but I haven't started tuning).

Is this normal for an AFR and O2 response at idle, or are my O2's shot (they were new last year)? At idle, I'm in fuel trim cell 16, long term counts are 123 on both sides.

Thanks,

Brent M.

 

I try to keep my idle as close to 14.7:1 as possible, generally it's about 15:1. This is using an FJO wideband.

For some reason your O2's are not heating up enough at idle. The heating elements could be on their way out or the power ckt has excessive resistance?

 

Stoichiometric, 14.7:1.