Vacuum leak/lean mix

Tiny
RICKD'S
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 170,616 MILES
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.
Sunday, June 13th, 2021 AT 11:02 AM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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

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Sunday, June 13th, 2021 AT 3:00 PM

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