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: 136,697 (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
16 people reported this problem
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Viewing 1 - 8 of 8 problem details
Diagnostic scan check - found engine misfire due to Intake Manifold Cracked and Leaking. No work performed at this time.
1992 Cadillac DeVille 123,000 mi,
It hasn't been fix
2004 Cadillac DeVille 87,000 mi,
SES light on, no rough idle . Threw codes P0171& P0174. Common failure, intake plenum gasket. Having it fixed soon!
1997 Cadillac DeVille 185,000 mi,
Hole on intake manafold
1999 Cadillac DeVille 175,000 mi,
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