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Cadillac DeVille Car Problems

Smog Check Failure Due to Excessive Carbon Buildup on Cadillac DeVille

Problem Description and Solution

Excessive carbon build up in the engine combustion chambers may be the cause of a smog check failure due to excess NOx emissions. A "top engine" decoarbonization cleaning procedure will commonly correct this concern.

(8 people reported this problem)

Problem Data

RepairPal Verified
Average mileage: 135,500 (113,000–158,000)
5 model years affected: 1991, 1992, 1993, 1994, more1995

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Brake problem? Or maybe a faulty head gasket cylinder?
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