Irregular idle after gas fill up

I have a automatic trans 99 XJ Classic. The other day, with 1/2 tank, I refueled with reg unleaded, as usual. On the way to my house, I noticed an irregular idle. I didnt think to much about it, but I did dump a bottle of gas treatment into the tank when I got home.
The next day, after starting it, the check engine light came on. I drove it to work which is about an hour away. 1/2 way to work, it began idling high and jerking when starting from a stop. At one stoplight, I put it in neutral and the tac steadily climbed rapidly and about knocked me into the steering wheel when I shifted into drive. I made it to work with it.
After work, I started it up and it idled low and cut out a couple of times. I tried disconnecting the Jet chip, with no change. I then took a pair of pliers and tapped on the TPS and IACM. I reved it from under the hood a little and it backfired each time. After, driving it around the parking lot and stalling out a time or two, I decided to chance the trek home, which was FINE! I HAD NO PROBLEMS THROUGH THE HOUR DRIVE HOME! Seems like it cleared up.
When I got home , I hooked my DTC tool to it and pulled the code P0121 throttle/pedal position sensor A circuit Range performance.
Some history, last summer, the jeep was idling a bit irregular after refueling and the same code came up. I replaced the TPS and cleared the code at that time and it has been fine until now.
What could be causing this problem again? Bad gas? Any suggestions as to what I should do? I appreciate it!
Mike

Seems too obvious, but how old are your plugs/wires/etc?

Bad gas...

Hard to say if the fillup is related but it is possible. What kind of fuel additive did you use? If there is water in the fuel which can happen, then an additive that contains isopropyl alcohol would be the most beneficial for absorbing the water. Don't know what kind of winter formulation fuel you guys use in Maryland but if you have 10% ethanol formulation, then don't bother with adding any more iso; there's already plenty of alcohol in there.

As you mentioned that you drive a couple of hours a day, let the tank get down to half again and then fill up (at a different station right?!) to dilute your mixture. See if that makes any difference.

It is not impossible that your TPS is faulty, even though you replaced it not too long ago. You'd be surprised how often that happens. However, it could be as simple as a contact issue. How about removing the connector from the TPS and cleaning it with electrical contact cleaner, then reattaching. The sensor is only as good as the contacts it is connected to....The fact that you are coding for a TPS though is significant.


Good luck and post back what you find!

Plugs, wires are about 2 years old.
I used Advance Auto gas treatment which is a little cheaper than the STP brand. Like I said, though, it began the irreg idle before I added this to the tank.