However, precise location varies slightly depending on the exact engine configuration. You'll need a repair manual specific to your vehicle's year and engine to pinpoint it accurately. A diagram in the manual would be invaluable. Searching online for "1991 Buick Park Avenue 3.8L engine diagram" might help you find one.
Caution: Do not attempt to locate or work on the CMP sensor without the proper tools and knowledge. Improper handling can damage the sensor or the engine.