My idle floats from 675 to 705. Throttle position reading is 16.9%. This at fully warmed up at 195 to 200.

it looks like mine is around 650-680 rpm and TP is 11%. At times it does sound like it's struggling, and the tac goes up and down just a little. Any suggestions would be greatly appreciated. Thx

When is the last time its had new plugs/tune up?

I would have said that's right around the normal (in gear) idle speed. My '98 XJ and my wife's '97 ZJ both sit right around that point.

I had an upstream O2 sensor that was reporting incorrectly. It did work, just not correctly. At the advice of this forum and another forum I bought a NGK brand O2 sensor from Autozone. The OBD system showed that the engine never went into closed loop and I got DTC P0138 indicating that the O2 sensor voltage was high. My scanner showed O2 sensor voltage at 1.0V,

I bought a WALKER O2 sensor and everything is GOOD.

And yet ANOTHER account of someone having success with the Walker brand O2 sensors.. Thanks for the feedback.

I bought a NTK sensor recently too. same thing, just read 1v. I went with a Bosch, problem solved. Those NTK sensors went down hill.

I replace the upstream O2 with . Now I"m getting P0172/P0175 System Too Rich Bank 1/2.

I'm thinking the O2 Walker is bad. Idles fine now but seems to drop sporadically like it's going to die.

Should I replace the O2?

Have you checked what the O2 sensor voltage is on your scanner?

Just in my internet reading I've come across the trend with the Jeep 4.0 that O2 sensors are like playing the lottery. NTK/NGK aren't what they used to be, although some have worked. Bosch is known to be good in general, although some weren't. Walker seems to the one works for folks when the others didn't. It could just be luck of the draw.