2003 Ford Ranger Engine Stalls

I have a 2003 Ford Ranger 4.0. When I turn on the air in any setting except the setting that just enables the middle vents(not feet or defrost), the truck will keep trying to stall. It mostly does it when it is in gear. I have replaced the plugs, wires, and air filter. It is not the A/C clutch because I also tested this with the A/C clutch disabled(I unplugged the A/C). I have also already replaced the sensor that changes the air flow to the engine when you turn the air on or off. A little more info, the mechanic that replaced the plugs did not space them right, so I took them out and re-spaced them. When I started it back up it stopped doing this, but it was miss firing in cylinder 2. So I replaced wires again, and the spark plug in cylinder 2, and the miss fire went away but the car is stalling again.