p0171 Problem

Question

I have a 2007 chevy cobalt ls coupe. have engine code p0171: fuel system too lean. i replaced the MAF sensor, down and upstream oxygen sensors and i have no vaccum leaks. where does the problem lie? this is a come and go engine code. its on for about a day and then next few days it shuts off. Only turns on if I am idle.

Answer 1

P0171 Fuel trim lean Bank 1

When this comes on is there any rough idle, ? Lack of power? If so this would be fuel pump related. If you dont have these when P0171 happens , This code is known to related to the EVAP purge system, where it take the fuel trim momnetarily out of its fuel trim.