Re: O2 sensor bad?
I see you say plugs are new, that was going to be my first suggestion. My next suggestion would be to check the air filter and change it if necessary. If that is good I would pull the intake tube and resonator box off the throttle body and give it a good cleaning. Wipe off the throttle plate and bore, make sure to open it by hand and clean the edges and back side. If it is really dirty I would recommend removing the throttle body completely and clean it thoroughly.
Also, remove the idle air contoller from the side of the throttle body and carefully clean off the end, making sure not to twist it. Also clean the idle air passage on the TB.
If an O2 sensor is really bad and sending a goofy fuel trim signal to the computer I think it could cause a rough idle and heasitation, and definitely poor fuel economy, but I'm not entirely sure on the idle part.
My Jeep: 2001 Grand Cherokee Limited, 245/65R17 Falken Rocky Mountain ATS, K&N drop in air filter, Bilstein HD's. De-badged, eagle-eye LED Tails & LED 3rd brake light, Addco front and rear sway bars, Superchips tuned & TM snip, interior 6k LED's, Gen3 ccfl projectors with Volt 6k HID lows, akebono brake upgrade with R1 Concepts premium rotors.