1991 GMC SIERRA
160,000 MILES
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ROCKLAND1969
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  • 1 POST
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
Apr 2, 2013 at 3:11 PM
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JACOBANDNICKOLAS
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  • 110,175 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
Apr 2, 2013 at 3:22 PM