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Cadillac DeVille Car Problems

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

Problem Description and 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.

(19 people reported this problem)

Problem Data

RepairPal Verified
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

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Brake problem? Or maybe a faulty head gasket cylinder?
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Viewing 1-8 of 8 comments
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!
Cracked Intake Manifold was causing a misfire. It was Replaced with an Aftermarket Dorman intake. (Least expensive option)