Check Engine Light Due to Intake Manifold Vacuum Leaks on Buick Lucerne

Problem Description and Possible Solution

An intake manifold vacuum leak can develop from a variety of sources, often causing illumination of the Check Engine Light with codes P0171 & P0174 stored. Thorough diagnoses will be necessary to pinpoint the cause in order to make the correct repairs. A "smoke" machine is often used to isolate the cause of difficult to find vacuum leaks.

Problem Data
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Average mileage: 76,219 (46,878–90,000)
Engines affected: 3.8L V6, 3.9L V6, 4.6L V8
4 model years affected: 2006, 2007, 2008, 2009
9 people reported this problem
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Bought the car used, engine light comes on for loose gas gap. Bought new cap, no change. Bought tool to reset which I do about once a month.