Don't know where to start

Ok, start by checking for any fault codes that may be stored in your trucks' computor. If you don't have a code reader, here is what to do.
1) take a 6 inch piece of speaker wire, and peel about a half inch of case off of each end.
2) the diagnostic terminal that you normally plug into is located under the dash, left side. About 3 inches long, 2 rows of holes 6 holes in each row.
3) Stick one end of wire into hole, top row far right. This is the ground terminal.
4) Other end of wire goes into hole beside first wire. Top row, 2nd from right.
This is the Diagnostic terminal.
5) Turn on ignition, but DO NOT START YOUR CAR.
Dash lights and bells will go on & sound. SERVICE ENGINE LIGHT will start to flash.
It will flash out any codes that are stored.
The start point is Code 12 (1flash, pause 2 flash)
It will do this code 3 times and then go to the next stored code. That code will flash 3 times on then so on. Once all the codes have been flashed Code 12 will flash again. Be sure to right down the codes and then have them deciphered.
TURN OFF YOUR IGNITION AND PULL OUT THE WIRE. DO NOT TRY TO START YOUR ENGINE WITH THE WIRE IN PLACE.
This is your starting point. If you do not know whats wrong with your truck, check for codes first!

IN THE FUTURE please let us know service history details, engine size (TBI, FI) tranny type etc.