hey all i have a 97 f150 that will not stop back firing ,but the thing is ,it is fine until after i hit about between 45mph and 70mph anyone got any suggestions ,also i have replaced the 4 wheel drive shift motor and it worked for about a day ,come to find out that the old one wasnt bad ,(found that out by hotwiring to the battery)worked just fine ,but it seems that my problem from what i can tell is that once i put it in 4 low it doesnt want to go back to 4 hi or even 2 hi i am almost wondering if what ever wire gives the motor power to turn backwards has a short,so if you know otherwise or anything that will help let me know

 

Check your plug wires. Probably had one come off. It was a common problem on mine when I had it.