Where are the back 4 spark plugs on a 1994 Cadillac eldorado?

The 1994 Cadillac Eldorado has a Northstar V8 engine. The engine is front-to-back in the car. Therefore, the "back" spark plugs are located toward the firewall (the back of the engine compartment). To be more precise, you'll find them on the rear-most cylinders, generally towards the back of the engine compartment.

You will need to consult a repair manual or a diagram specific to the 1994 Cadillac Eldorado's Northstar V8 engine. Accessing those rear plugs can be tricky due to limited space. A repair manual will show you the exact plug locations and the best way to access them. Trying to locate them without a proper diagram is highly discouraged, as you could damage other components.