Where are the spark plugs on a 1999 Chevrolet Malibu with 2.4L L4 Engine?

On a 1999 Chevrolet Malibu with the 2.4L L4 engine, the spark plugs are located on top of the engine, under the plastic engine cover. You'll need to remove the engine cover to access them. They're generally arranged in a line, one for each cylinder. Consult a repair manual or online diagrams specific to that year and engine for the precise location of each plug. A diagram will show you their placement and firing order.