P0171 Chevrolet -

Question

Engine has rough idle on cold mornings, but returns to normal after it warms up. then runs fine for the remainder of the day. code reads po171 and po174.

Answer 1

Hi there,

These codes are both lean codes for both banks on the engine. This usually means an issue with low fuel pressure, and intake manifold vaccum lean or a faulty mass air flow sensor. Because it is affecting both sides of the engine these items need to be checked.