Why would I have slack in my throttle cable

That will not prevent the engine from starting. You can take the cable off completely but the Engine Computer is still in charge of idle speed. All engines will produce a nice "idle flare-up" to around 1500 rpm, but Fords are typically lazy and take a long time to come back down to around 800 rpm. That is automatic and has nothing to do with the throttle cable.

If you feel there's too much free play in the cable, look at how it is attached on the throttle body. Some are held in a clamp that can be loosened, then you can pull the cable tighter. The only symptom that will cause is you'll have to push the gas pedal further to the floor than normal.