12 is 5.5% rich, 13 is 2.3% lean and 14 is 10% lean. The AFR will hit those numbers depending on various engine load conditions. Is the 13-14 at idle constant ? You had a problem that was fixed with O2's a while back that indicates the ECM is running 'closed loop' and it is constantly altering AFR to hold 12.7. Whatever you do to the engine (change cam, etc) the ECM will always try to hold 12.7 by adding or pulling up to 15-20% or more fuel. During those abnormally high AFR corrections the engine usually runs crappy w/idle, acceleration of idle problems. That's why tuning (timing, VE and TBS) after a cam is required. The only way around ECM AFR control other than 12.7 is a 'closed loop' tune. My guess is either: 1 - if your WB is accurate then one of your O2's is reading 3-11% rich due to bad O2 in one bank and it's pulling 3-11% fuel in error. -OR- 2 - the WB may be reading a tad lean at certain conditions. Is the the 12 during acceleration, deceleration or cruising ?
I'm Bob.. 1994 Z28, A4, Stall, CAI, Cam, RR's, 342 rear, LT's , CatBack, Tuned
Last edited by bobdec; 11-13-2012 at 09:20 AM.