Vacuum leak/lean mix

1997 CHEVROLET SILVERADO
170,616 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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RICKD'S
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BlueDriver scan shows:
P0131 O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
P0171 System Too Lean Bank 1
P0174 System Too Lean Bank 2

O2 sensor has already been replaced.
On trip 3 hours from home in the Poconos (Sciota Pa) checking oil I forgot to put the oil cap back on.
Jun 13, 2021 at 11:02 AM
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ASEMASTER6371
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Good afternoon,

Do you have a scan tool that can read the long-term trim percentages?

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

When you have the engine running, can you feel a vacuum at the oil fill? That would indicate a leaking intake manifold gasket.

https://www.2carpros.com/articles/replace-intake-manifold-gasket

Check your PCV valve as well and make sure the ball rattles in the valve.

Check the fuel pressure. Low pressure will cause this issue. You can rent a tester at a parts store.

Central SFI .................... 60-66 psi
SFI .................... 56-62 psi

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

All the codes indicate lean running from either a vacuum leak or low fuel pressure.

Roy

Jun 13, 2021 at 3:00 PM