so i picked up a 91 si the other day and it didn't have the stock a6...
it came with a b2 block and a pm9 head. what engine harness do i use? mpfi btw.

 

Lol thats a funny combo. Well whoever owned it before you basically just downgraded it from an Si to a Dx(block) and STD (head). So it should be running a Dx engine harness. And are you sure pm9 and not pm6? You said its mpfi so mabye Dx engine running an si intake mani and harness idk....

 

that's what i was thinking lol, stupid swap.
yeah i'm sure, head reads pm9-1.
so use a dx harness?

 

You NEVER use the engine harness to match the motor... (unless you love many hours soldering and heat shrinking). Especially if you are already have an Si, as the plugs and pinouts are not the same. If you look by the passenger shock tower you will see 3 plugs rather than the DX/STD 2 plugs. Always use the harness that matches the car and modify it as necessary.

 

Ok what I was trying to say is that if you have an Si intake manifold on the Dx/std engine then it should be running the si harnesses(cabin/engine). But if it has a DPFI intake then you could do what he said and modify your si engine harness(if its still there) or the harder way would be to change the engine and cabin harness to a dx.

 

ah, thanks guys. i was gonna get a dx harness too.
time to search for an si harness now.

 

ummmm. still no. if you have a dx/std manifold on the motor, just get an mpfi manifold and make sure the distributor matches up to the ecu. then your set. no need to modify anything.