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.Google+
Car Problem Reports
Buick Lucerne Check Engine Light Due to Intake Manifold Vacuum Leaks
Buick Lucerne Problem
Engines Affected: 3.8L V6, 4.6L V8
Average Mileage: 68,439 mi (46,878 mi - 90,000 mi)
Check Engine light comes on and stays on. Does not flash, just stays steady lit.
Visitor, 2007 Buick Lucerne, 3.8L V6, 90,000 mi
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.