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.
Check Engine Light Due to Intake Manifold Vacuum Leaks on Cadillac DeVille
Average mileage: 130,659 (11,700–187,000)
Engines affected: 4.6L V8, 4.9L V8
15 people reported this problem
7 people shared problem details
Diagnostic scan check - found engine misfire due to Intake Manifold Cracked and Leaking. No work performed at this time.
1992 Cadillac DeVille123,000Visitor
It hasn't been fix
2004 Cadillac DeVille87,000Visitor
SES light on, no rough idle . Threw codes P0171& P0174. Common failure, intake plenum gasket. Having it fixed soon!
1999 Cadillac DeVille175,000Visitor
Cracked Intake Manifold was causing a misfire. It was Replaced with an Aftermarket Dorman intake. (Least expensive option)
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The EGR control solenoid or EGR valve may fail causing the Check Engine Light to illuminate.
Illumination of the Check Engine Light may be the result of a loose or worn gas cap.