Therefore, the number 1 plug wire goes on the number 1 spark plug. To locate #1 spark plug, you'll need to consult a diagram in your owner's manual or a repair manual specific to your 1986 Mustang 3.8L. The #1 cylinder is typically at the front of the engine, on the passenger side (right side if you're looking at the engine from the front). However, *always double-check with a diagram* as variations can exist.
