The problem is now fixed.
Before installing the new O2 sensor, I removed the electrical connector and started the car. To my surprise, I did not get a check engine light but I did get plenty of black smoke as usual.
I did not have an O2 sensor socket, so I used a 22mm open end wrench and it came out easily. The exhaust pipe was warm, so that may have helped in removing it. The new sensor already had anti-seize on it, so I screwed it in after cleaning the threads. The hardest part was getting the electrical connector back in place, there is no room to get your hands on it.
Now for the good part of the story.
I started the Rodeo and let it warm up and I got plenty of black smoke when revving it up! I was disappointed to say the least. I sat there and thought about what else could be wrong. It may be time to go to the dealer.
While sitting there, I thought I might try resetting the computer. Easy to do, but I really didn't think it would make any difference. I pulled the fuse and waited 15 minutes. After starting the car, it sounded different and better. I revved it up and saw lots of brown smoke coming from the tailpipe. Hmmm, could this be it?
I threw the dog in the back and went for a spin. I floored the pedal and you could not believe the amount of brown smoke that came from the tailpipe. I did this several times until it cleaned out the buildup from running too rich. Then I went on the highway and did a full throttle run. The off idle hesitation is now gone and the engine purrs.
After returning home, I looked at the inside of the tailpipe and found it was turning a brown / grey color. The pipe has always been sooty black with carbon as long as I've owned it. I think I'm going to pour a bottle of seafoam in the tank and fill it up to check the mileage.
I need to run it some more today and see if the surging problem has gone away as well.
Happy with the Rodeo again (for now),
Dale