Where are the spark plugs on 1992 Oldsmobile Achieva?

The spark plugs on a 1992 Oldsmobile Achieva are located on the top of the engine, under a plastic engine cover. To access them, you'll need to remove the engine cover. The exact arrangement will depend on whether you have the 2.3L 4-cylinder or the 3.1L V6 engine. They'll be in a roughly inline arrangement in the 4-cylinder and a V-shaped arrangement in the V6.

Because there's a bit of variation, and you'll need a shop manual or a good diagram to be certain of the precise location of each plug and how to access them without damaging anything, I strongly recommend you consult a repair manual specific to your 1992 Oldsmobile Achieva's engine. A Haynes or Chilton manual is a good place to start. You can find diagrams online as well, but using a reliable manual is safer.