Question about wiring: quite sure I've been told that for an LS swap the wiring harness that comes from the computer through the firewall is not needed and can be removed. What are the wires here (circled in red) attached to the side of the computer? I would rather not cut wires just in case something is needed but want a cleaner look as well. Pics also show where wires go through the firewall. In the engine bat, the wire circled in green just has a clip on the end, but it traces back to the driver's side so I'm not quite sure what to make of that.

Thank you!!!

 

If your car is an 84 than yes,..... your on the right path.

Those connectors are the 'C207 'dash-to-ECM harness connectors. Start at that spot and unplug them from the dash harness, then unplug the ECM. There is a large plastic clip that holds the ECM harness in place thru the body behind the pass kick panel; remove that clip, push the 'TAB' on the wire bundle and push the bundle into the fender well along with the wiring and C207 plugs. ( removing the fender liner - at least most of the way - makes the next step easier. ) Inside the fender well there is a plastic wire loom C-clip holding the ECM wire loom; remove the loom from that clip, then snake the entire ECM harness into the engine bay. The wire bundle WILL fit thru the hole in the engine bay/fender well,... it has to be positioned just the right way,.. but it WILL JUST fit thru the hole.) Once everything from inside the car is in the engine bay just unplug each of the plugs on that ECM harness from the SMOG stuff, auto tranny (if equipped ) and other wiring under the hood - done.

You might loose the oil pressure sending unit wire,... (it travels in the ECM harness in some cars) and you will loose the TCC lock-up at the tranny (if automatic ), or the reverse light wiring ( if stick). Those should be about the only things you will "loose" other than smog & CC carb/distributor related wiring.

Here is the C100 (Engine harness) and C207 (ECM harness) info for your 84:



1984 C207
PIN Color From / To (Notes)
A Brn ALDL / ECM (AIR control)
B Dk Blue BU Fuse / Back Up Switch ( T5 only )
C Wht/Grn Light Driver / ECM
D Tan Oil Pres / Gauge (L4)
E Wht/Blk ALDL / ECM (test)
F Pnk/Blk IGN fuse / EGR-ECM
G Lt Green BU switch / Rev Lights ( T5 Only )
H Tan/Blk ALDL / TCC-ECM
J Org ALDL / ECM ( L4)
K Brn ECM / VSS
L Tan/Wht Fuel Relay / Fuel Pump ( L4 )
M Blk/Wht VSS, P/N switch / Grd
N Org/Blk ECM / P/N switch
P Ppl Brake / TCC ( V8 )
R Ppl Crk Fuse / EFI (L4)