Is it normal for the O2 sensor to register 4 mV at *any* time? When I'm cruising at ~60 mph and let my foot off the pedal the O2 sensor (through AutoXray) reads 4 mV until I get down to around 45 mph, then starts to oscillate like normal between 200 and 700.

I'm currently having a problem with running too rich and hunting idle. I've checked the EGR, PCV, leaky injectors, fuel pressure and this is the next step for me to try and find out what's going on.

Thanks.

 

i'd have to look in my manual to be sure but i think 8mv is "normal" but it does change up and down with engine load and speed