I amnew to this thread looking for some help with someserious problems. my truck is a 2003 Gmc 2wd 4.8l auto trans. the guy i bought the truck from said he was driving the truck and it started skipping 2 years ago so he parked it he was told by a friend that the head gasket was blown. So I bought the truck and the fuel pump had to be replaced before i could start it. now when i get it to start it is skipping severly has lots of blowby and no power at all. the only code is p300 random misfire. there is no water in the oil and the owner said it never ran hot. it sounds to me like it has jumped timing. what do you guys think? i am just wanting some poinions before i start putting parts on that are not needed. the truck has 76000 miles on it

 

how much blowby? because that would lead me straight to bad rings

also try to test and replace coils plugs and wires before you try to redo the timing.
if im not mistaken these trucks use a chain which is pretty hard to jump time on

also check your catalytic converter to see if any of the 2 are plugged, that will cause the exact problem you are saying and will throw that code

 

Thnks I will check all of that and let you know what I find