OK, my car is running very very rich at idel. 1400 ppm of HC. Its a 95 z28 with 355 , cc305, gutted cat and a tune via lt1 edit. My air fuel gauge (auto meter) reads rich and then goes crazy after aout 30 secs of run time. Bouncing from very lean to very rich. How can tell if it is my O2 Sensors?

Thanks

 

Its completely normal for the O2 readings to bounce from lean to rich when the PCM goes in to closed loop. That's part of the closed loop control. The problem is the extremely rich startup. Do you still have the AIR system?

A gutted cat results in high levels of unburned HC's, CO and NOx..... that's what the cat is there to control. Did you get the 1400ppm value during a smog check? Running rich can be the direct result of misfires and exhuast leaks before the O2 sensors - got any of those?

 

My car is running rich as well. And i thought that it might be the o2 sensors as well. My mods are below. As well as an offroad pipe, No AIR or EGR. The car stubles about 2000 rpms when the converter locks up. At WOT there is no miss and runs fine all the way to 6500. So could this be the o2's?

thanks
Dan