An ignition coil may fail causing one of the cylinders to misfire. Each of the two banks of cylinders has its own coil assembly. If one ignition coil fails the coil assembly for the corresponding cylinder bank must be replaced.
Car Problem Reports
Cadillac Seville STS Misfire Due to Failed Ignition Coil
Cadillac Seville STS Problem
Average Mileage: 113,250 mi (84,500 mi - 167,000 mi)
Visitor, 2001 Cadillac Seville STS, 102,000 mi
mpg dropped 1-2mpg, then rough acceleration, then misfire code
suggest replacing spark plug boots USE LOTS of dielectric grease
Visitor, 2003 Cadillac Seville STS, 132,000 mi
check engine light due to coilpacks misfiring
Visitor, 2000 Cadillac Seville STS, 167,000 mi
rear coil went bad replaced it and ive been fine.
Visitor, 2003 Cadillac Seville STS, 84,500 mi
One cyclinder misfires according to the computer diagnostic readout 14,000 times!)It is in the shop now.