Will a D16y7 fit in a D15b7 1994 Honda Civic?

Answer 1

Physically, yes, it'll drop right in. The engines are nearly identical, aside from the displacement. Electrically, however, you have do to some work to get it running. If you choose to keep the existing OBD-1 ECU, some of the sensors may be in different locations or may have different plugs. If you swap over the OBD-2 ECU and harness from the donor car, you'll have to add a second O2 sensor behind the catalytic converter. I'm afraid I don't know the exact differences between the two engines when it comes to that though. Hopefully somebody else does. You'd be best off picking up wiring diagrams for your 94 and for a 1996-2000 Civic DX/LX (which is what the D16Y7 came in originally).