e30 or e34 harness?

[n3nyongmini]

OK here's the goods:

I have a complete '90 e34 m30b35 going into an '89 325i.

The m30 harness was cut by the PO just after the flexible rubber cover/boot that is next to the hard plastic injector harness cover.

The m20 harness is complete except for the oil pressure sender wire (lazy and cut it) and attached to the car/ECU etc.

As I see it, I have three options for wiring the m30:

A. Cut the m20 harness at about the same place and splice the m30 harness to it, using Frank's write-up to match wires and place all the splices under the flexible rubber cover/boot.

B. Remove the m30 harness and use the m20 harness, lengthening wires as needed.

c. Get an un-cut m30 harness and replace the cut one. But will I need to do some splicing to connect with the rest of the e30 wiring anyway?

What's your thoughts, Fellas?

[slammin.e28]

I'd just use the M20 harness and lengthen wires.

[SpeicherBimmer]

I'd just use the M20 harness and lengthen wires.

+1. That's what I did and it made things so much easier. The B35 harness might look a bit prettier, but the M20 job isn't bad at all and is pretty much PnP.

[tfritz]

I attempted using the m20 harness for my swap but had surging issues. Switched to the m30 harness and had no problems.
I know at least one other member had a surging problem with the m20 harness, just one thing to consider, but many use the m20 harness with great results.

[James Crivellone]

I just use the E34/E32 harness. Looks factory, just need to repin C101 (if its an 88/89 735iL) or crimp on a new C101 to replace X20 (E34/Late E32)

I'd rather cut / crimp a new connector versus adding splices to the harness.

my

[csermonet47]

M20 harness for days. Here is mine:





I cleaned up a bit more since then but it required barely any modification at all and is already the shape to fit the E30 bay. Get some harness tape and nobody would ever know it isn't factory. Plugged everything up, popped in the ECU and everything works perfect. All the gauges and everything. The car just thinks it is an E34.

Remove the M30 harness from the injector box and dremel it out to make the M20 harness fit:

M20 harness is the only way to go in my book.