99 GMC Sierra SL v6 sometimes does not want to start, does crank. Any ideas?

driftcris

Usually doesn't start in the mornings and sometimes after I go to the store turn off the truck then try and turn it on cranks but doesn't turn over. Does start and run after couple try but starts rough 

rusty_cage

sound like air fuel mixture is not regulating properly. have you had the injectors cleaned? do you change the air filter regularly ? O2 sensor also. I would start with cleaning injectors and filter. how many miles r on it? and how many miles on the plugs