Smog Check Failure Due to Excessive Carbon Buildup on Cadillac Fleetwood

Problem Description and Possible 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.

Problem Data
RepairPal Verified
Average mileage: 84,000 (84,000–84,000)
4 model years affected: 1990, 1991, 1992, 1993
6 people reported this problem