Smog Check Failure Due to Excessive Carbon Buildup on Cadillac Seville STS

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: (–)
2 model years affected: 1991, 1992
2 people reported this problem
Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews