The engine control module (ECM) electrical grounds on the front of the engine block may have high resistance causing a rough running engine or stalling condition.
Car Problem Reports
Cadillac Fleetwood Performance Issues Due to Faulty ECM Grounds at Front of Engine
Cadillac Fleetwood Problem
Visitor, 1991 Cadillac Fleetwood, 140,000 mi
Runs fine, the all of a sudden, begins to run rough, rough idle, stalls when stopped or in turns, check engine light comes on only when on highway, sevice soon light on sometimes. 2 different mechanics couldn't find problem.