Idle drops after engine warms up.

[Ecomike]

It is premature to replace the O2 sensor. It is however very useful to get data from the working O2 sensor at idle and at 2000 rpm, and to test the wiring to the sensor to see if the 12-14 volts is even getting to the O2 sensor heater that it needs to work at idle. Also that same wiring is prone to road hazard and drive shaft and exhaust manifold damage and carnage (proximity issues), so he needs to follow your direction and find it and inspect the wiring.

OP: Google some you tube videos, they are great these days for rapid show and tell "HOW TOs" on various tests and repairs and part swaps, like using a digital or analog VOM, and swapping sensors.

Number of O2 sensors varies by year but the '93 has only one and it is very easy to find and replace.

I just replaced the one on my '93 with an NTK unit. Get the drivers side front up high enough to get under (ramps will do) and you can't miss the sensor screwed into the exhaust pipe. It has a cable leading to the left to a connection supported by a metal bracket. Unplug and remove the old sensor and follow directions that come with the new one as to proper installation torque.

I would just replace the sensor unless you are sure the current one is relatively new. I had a Bosch unit before but the consensus seems to be that the NTK units are the best.

Not that I necessarily stick with the consensus as I also went back to Bosch platinum plugs after giving the Champion coppers a more than fair tryout. Mileage is back up to ~21 and all is well, at least with this aspect of XJ ownership.