I have been running around this issue for a while now of my oxygen sensor jumping between.92-4.96 volts ever since I changed it. No matter what I Am at, idle or going down the highway it always jumps up and down randomly. I have read many post by Ecomike and his seems to differ from my readings. His seem to stay between 2-3 if i recall correctly at 2500 rpms. My mileage has always sucked, average about 160 miles to a full tank and alot of that is highway. The question is, is it the o2 sensor that is funny or do i have another problem. ( ALL TEST DONE RUNNING TEMP )The loop status is closed, and the scanner jumps rich to lean continuously at idle or driving on interstate. Map voltage at idle is 1.7-1.8v, Throttle closed reads 13% on scanner. TPS is adjusted to 83%. Coolant is at 88c, Spark advance at idle is 14-16 degrees, knock sensor reads 0 at idle will go up if i accelerate. Egr will open under acceleration, but closes on idle. O2 sensor continuously goes from .92-4.96v all the time, idle is about 580-620. Jeep is an 87 4.0 Renix. Thanks