2008 F-150, 4.2 V-6, Auto w/air, 171,000 miles.I will get and engine miss someti

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2008 F-150, 4.2 V-6, Auto w/air, 171,000 miles. No check engine light, no codes. Problem; I will get and engine miss sometimes 2 to 4 or 5 at slow speeds. I may drive 1 to 450 miles and nothing happen. It will miss more often after driving 300 miles at 75 to 80 mph and slowing down to 35 > 45 mph, but not consistent. I may drive around town for 4 or 5 days and nothing and then it will happen 3 or 4 times. I checked for vacuum leaks, I thought maybe water in the gas ran many gas dryer fluids, thought maybe dirty injectors used those fluids also and changed the air cleaner. Any could cause this but most would have cause code also.