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OBD1 M52 - o2 Wiring & Rev hangs

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    OBD1 M52 - o2 Wiring & Rev hangs

    Hi all - my first real "help me" post in this community, hope that you folks can help shed some light for me!

    I got my hands on an OBD1 M52 swap'd track car that's turning into a real basket case. The car didn't run when I got it, and now starts and drives thanks to a new crank position sensor and fuel pump; but I've been re-doing sections of the wiring harness, as the PO ran the main bundle behind the block and parts melted due to heat and consequently shorted out

    A M50 wiring harness was used, I assume to convert to OBD1 (it's an older build, from what I understand).

    There's only one o2 sensor which is downstream from some sort of "shorty" headers - about halfway down the car. I've consulted the wiring diagram from "wedophones" (page 105) for a '93 M50, I'm not clear if the following wiring for my o2 is correct:
    1. yellow running to pin 13 of DME (PO had t'd into this wire to run to an AFR gauge which now works since I repaired this wire)
    2. black running to pin 40 of DME
    3. green/purple to o2 heater relay
    4. brown to chassis ground
    5. non-jacketed (I think part of the foil shield?) runs to a junction which then runs to both crank position sensor and an orange/brown wires going to pin 28 of DME

    My question - the connectors for the o2 sensor have only 4 positions - the 5th wire which is non-jacketed, is this right? Should the 5th wire be contiguous with the ground pin of the o2 sensor connector (wire 4)?

    Right now the car idles at around 1200rpm (I believe that's normal due to the pink injectors and light flywheel) but it will surge/hang revs when I give it a bit of gas from idle. I may be chasing the wrong thing to solve this issue, but I've got to start somewhere!

    Thanks fellas!
    Forgive me, I used to race a Honda.

    from looking at page 105, your description seems to be correct. but it looks like the wire going to pin 2 of the heater relay is green and then switches to green/blue. but maybe i'm looking at a different manual. as far as the shielding yes i think that's part of the foil shield that should be wrapped around all 4 of the o2 sensor wires. as far as how it connects to the wire going to pin 28 of the dme i'm not sure since i've never had to get that far into the harness. i think as long as its making contact to ground it should be fine. as far as a high idle i don't think a ltw flywheel would cause that, and may actually cause the opposite effect due to less mass/inertia? to keep the engine spinning. i would start with checking for vacuum leaks and that the throttle cable is not binding and that the po has not tampered with the throttle body stop adjustment