I've got 2 codes that fall hand in hand with a common issues on the z's. We have all heard that t/ps or hfc's cause the a/f ratio codes. Normally its always one or the other but for me its both. Yea I know you have read it a bunch of times but my bank 2 is rich and 1 lean. Even before I started replacing parts I still got the same codes. The car runs fine even through the ses light (which I'm ocd abou). Can anyone possibly explain the logic behind this? I've read the only real fix is a custom tune, fine. But can I fix this?

Replaced the maf, bank 2 (down stream) O2, crank and both cam sensors (for slip light), exhaust system (minus headers). I'm not throwing any more money at this till I do a couple more mods to make a tune worth it

 

i would run some seafoam through your fuel system to try and clean out injectors. if you replaced the cats make sure header and cat bolts are tight and gaskets is good. if u didnt replace cats make sure they not clogged. usually a bad o2 will read lean. double check your plenum manifold gasket is solid and torqued to spec. if no air leaks anywhere (all hoses and exhaust) swap your upstream o2s to eliminate a bad o2. hows idle?

 

It had t/p's on it when i first got it but the t/p's were such poor quality that the weld spots cracked over time causing me to loose a sensor during driving. Hence my invidia hfc's now. Its got the stock headers on it judging from all the oxidation. Ill be adding a plenum spacer if i have to take anything off. But i have verified there are no intake leaks via the ol carb spray method. And oh seafoam was one of the first things i did when i got the car so done and done