2013 Chevy Silverado P0171 and P0174 Lean Both Banks - Hesitation on Acceleration

Question

My truck is throwing both P0171 and P0174 lean codes and it feels really sluggish when I take off from a stop light. I can hear a slight whistling sound coming from the top of the engine when it is idling in the driveway. It seems to run a bit better once I get up to highway speeds but the fuel trims are still way off.

turbo_tony · Accepted Answer

The issue was a cracked PCV tubing assembly and a leaking intake manifold gasket. I replaced the intake manifold gaskets with the updated Fel-Pro MS97204 set and installed a new PCV hose (Part #12617138). After torquing the manifold bolts to 89 lb-in in the proper sequence, the long term fuel trims returned to +3% and the whistling stopped completely. The total cost for parts was about $85 and took 3 hours to finish.

torque_terry · Answer

Check your intake bellows for cracks, especially in the bellows sections after the MAF. Also, spray some brake cleaner around the intake manifold gaskets while it's idling to see if the RPMs jump, which indicates an intake leak.

Carlos Diaz · Answer

The whistling sound is a huge giveaway for a vacuum leak. Check the PCV hose and the EVAP purge solenoid. If the purge solenoid is stuck open, it will pull unmetered air into the manifold and cause these lean codes.

Sarah Thompson · Answer

Since you have both banks lean, it is usually something that affects the entire fuel map like a vacuum leak or a failing fuel pump. Check your fuel pressure at the rail; you should be seeing around 55-60 psi.

2013 Chevy Silverado P0171 and P0174 Lean Both Banks - Hesitation on Acceleration

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