Problems with 91 Ford F150
 

Me and my dad bought an old 91 ford f150 4.9 v6 i think, and we've put some work into it, New tires, new fuel pump, new drive shaft, but I've had this same problem with it that i can't figure out and it keeps getting worse and now its broken down again. For some reason it keeps jumping "out of time" my dad would say and we would have to readjust it. at times it'll do this and the rpms will drop, and i won't get the maximum power, i can only get say 1000rpms and slowly climb and my check engine light comes on, and alot of times it'll shut off if my foot isn't on the gas while i'm at a red light. We believe it's electrical or the timing chain, also the muffler is off and my dad says something about no back compression on some vehicles can cause the shutting off. Help??

I would pull the codes on it and see why the check engine light is on

Check the cotter pin that holds the gear onto the distributor. If it snapped the gear will spin and cause the engine to keep going out of "time"