Hi scotty, I have a 2001 Chevy Silverado 5.3 l four-wheel drive automatic with 287,000 MI. This happens mostly in cold mornings. It'll run a little rough and I will get a P0171 and P0174 lean condition codes. When I hook up a scan tool, I noticed my long-term fuel trim on both Banks is high (10%-13% at 2,500 rpm's and goes down very little of at all at idle). Could this be bad oxygen sensor? Bad injectors? I'm stumped.
Watch your long term fuel trims while you're going down the freeway... If they drift back toward zero, that indicates the problem is likely an air leak to the intake manifold, maybe intake manifold gasket, PCV valve, power brake booster leak, etc. If the fuel trims stay high at speed, that looks more like a fuel delivery issue like low fuel pressure, or cruddy injectors.
