I have a 3-wire Mopar O2 sensor on my Shelby Lancer. It seems to be very innacurate at WOT; which isn't very surprising considering it's narrow-band and doesn't have a sensor ground like the 4-wire O2 sensor.
About a year ago I had the car on a dyno with a wideband sensor up the tailpipe. The car does not have a catylitc convertor BTW. The wideband sensor showed the mixture was extremely rich as soon as the car spooled up. So rich it was that the A/F went off the scale. My autometer was showing 18 lights.
Seems like 18 lights is as rich as it will show, even though the wideband was showing it to be extremely rich. I'm thinking that the 3-wire sensor doesn't have a very good ground path which is pulling the output voltage down. Is there anyway I can make the ground better for the 3-wire sensor or is converting to 4-wire the best fix? If I convert to 4-wire O2, where should I attach the extra ground? Should I splice it into the sensor ground circuit that the other sensors use, or should I just run it to the cylinder head or (-) battery terminal?