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2001 GMC Sierra 1500 pick up 4X4 Question a.

Tiny
ROCKLAND1969
  • MEMBER
  • 1991 GMC SIERRA
  • 160,000 MILES
2001 gmc sierra 1500 pick up 4x4 Question a code po171 that keeps comming up ever six mo. Cant not locate vac. Leak. Did smoke test on heads, did ful tune up top to bot. Had my mac. Look at it 2 times cant find prob. Also have a bubbling noise comming from truck located by plastic by cabin filter housing. Sounds like something leaking but no leaks comming from truck?If any one has a clue please send me some feed back. Thanks
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Tuesday, April 2nd, 2013 AT 3:11 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
You have a lean mixture. The following is a list of possible solutions:

†Clean the MAF sensor.
†Inspect all vacuum and PCV hoses, replace/repair as required
†Inspect all hoses and connections in the air intake system
†Inspect and/or test the intake manifold gaskets for leakage
†Check for a dirty fuel filter and proper fuel pressure
†Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
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Tuesday, April 2nd, 2013 AT 3:22 PM

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