I have been having a problem with the stupid SES light coming on. First it said system too rich bank 1. So I replaced both o2 sensors and decarboned the engine. Now it reads both banks are running too rich. What the hell! The car idles and runs perfectly. It starts right up in the morning and accelerates perfectly. I dont see anything wrong with the way it is running. But I keep getting codes. So I just keep resetting the computer. And after about 1 week or 2 the SES light comes back on saying I am running too rich again. Sometimes the SES light will come on for a day then go away. I don't have too many modes on my Z. I have ported heads and a 5 angle valve job. I have a SLP air induction system. And my cats are gutted. I put O2 simulators on the convertors. Other than that stock cam and manifold. The engine purrs like a kitten. Does anybody else have this problem? Thanks for the help.

 

Maybe a tune to lean you out?

 

Put a scanner on it, and see what the long term fuel corrections (BLM's) look like. I'll bet they are down to 108, can't go any lower and the PCM is still sensing a rich condition. If that's the case, you need to look for the cause, which may be something other than the O2 sensors. Are you running an aftermarket cam with the "ported heads"? Are you using stock injectors? Any sort of PCM tuning been done? Have you checked the fuel pressure? Have you checked for a saturated EEC canister? Have you messed around with the MAF sensor?

Might also want to mention the specific year of your car.... you mention using O2 sims, so we can assume you have a 96 or 97??? By why make us guess???

Sometimes the SES light is a little smarter than you might assume.