Originally Posted by FocusRus
Cindy, your problem is in the spark plug, plug wire or the coil. It explains the misfire over 40 mph, and why the MIL came on when you turned on the AC.
This new guy is probably right (although I don't see how the AC operation would effect a single cylinder), the fact that the misfire happens only after a certain engine load and not at all times means it's probably a specific ignition component and not a problem with the voltage feed or input to the ignition system. It's possible the fuel injector for #2 isn't working right but I doubt it, that would be rare.
If you can live without the car a few days all new ignition components (coil pack, wires, and spark plugs) could be bought online for less than $100, and I think would solve your problem without getting into further diagnosis, the existing stuff isn't all bad but further complicated diganosis would be needed to narrow it down.