they don't fall off themselves as they clip/snap the connection. whoever worked on your car last accidently left a wire loose from your coil pack. have you had a tune-up done recently?


each cylinder on your car has 2 spark plugs, they take turn firing first as they alternate back and forth, so it fires a then b on one cycle, then fires b then a on the next. so you still have combustion, just retarded on that cylinder half the time. The other time the extra unburnt gasses go out the exhaust, or rather in both cases.