Check Engine Light Due to Intake Manifold Vacuum Leaks on Cadillac DeVille

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.

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Average mileage: 124,957 (11,700–187,000)
Engines affected: 4.6L V8, 4.9L V8
9 model years affected: 1991, 1992, 1994, 1995, more1996, 1997, 1998, 1999, 2004
14 people reported this problem
6 people shared problem details
Diagnostic scan check - found engine misfire due to Intake Manifold Cracked and Leaking. No work performed at this time.
SES light on, no rough idle . Threw codes P0171& P0174. Common failure, intake plenum gasket. Having it fixed soon!
1999 Cadillac DeVille175,000
Cracked Intake Manifold was causing a misfire. It was Replaced with an Aftermarket Dorman intake. (Least expensive option)
Engine need servic cod#10174
check engine light comes on while driving
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