Running too rich?
 

Ok, here's the deal....'00 Civic EX (D16Y8) Intake, cam gear advanced 2deg., race cat w/O2 sim., Apex'i N1 catback, MSD 6AL ignition, AEM fuel rail and pressure regulator, Apex'i VAFC. I ran into this problem shortly after installing the O2 sim. on the secondary O2 sensor. When the engine is under load, cruising between 2000 and 4000 RPM, my AFR guage registers lean (somtimes not even registering). The car stutters until either A.) i let off the accelerator or B.) the air/fuel mix restablizes. I've replaced my plugs, fuel filter, tuned the VAFC, and checked the ignition sys. but to no avail has the problem been fixed. The ECU is throwing a "primary O2 reading rich" code. The only things that I'm left with that I can think of is the injectors (possibly sticking), MAP sensor, and TPS sensor (since the latter two are used determine the A/F mix narrow throttle). Basically I'm looking for a little bit of input as to what all might be causing this and how to fix it. If anyone has run into this pblm. please speak up.

Thanx
Josh

i know if you have a obd2 and you don't bypass the 2nd o2 sensor correctly, it will run super rich to protect the engine

if you got a race cat , that might be you problem

Usually you can tell if you're running rich by just pulling your plugs and looking at the bottom of them. If they're black you're running rich.