BTW this started after I filled up with gas, (name brand).
When you say that, do you mean that you stopped for gas, filled up, re-started your TJ, and it started running rough? If so, did the rough running stop when you started driving or did it continue? Finally, if it continued, but eventually cleared up, it's not likely the IAC, but rather the EVAP/Purge Solenoid. Keep reading if so. Otherwise, if the rough running only occurred at idle and never resolved itself, the IAC is a likely culprit.
You can download a Factory Service Manual from the TJ Resources section
here on the forum. When you do, you'll find a description of how the thing works on pdf page 1665, along with this picture of where it can be found (it's #2) on pdf page 1666:
The EVAP/Purge Solenoid is an electronic valve that the EVAP system (coded into the logic of the PCM) uses to dump fuel vapors from the charcoal canister to the intake manifold at certain times, to burn those vapors up instead of releasing them into the air. The problem is that the solenoid can fail in the open position, and then, when the PCM runs in open loop, the engines runs rich, and that causes the rough running. It's especially evident after filling up because the refueling process stirs up a lot of vapors in the tank and vent system. It eventually clears up because either those vapors get completely burned up as you drive or the system goes into closed loop at some point and the O2 sensors pick up the rich condition and the PCM reduces the injector pulse-width to get back to a proper air/fuel ratio.
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