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O2 Sensor Connections on an 86TR

Discussion in 'Technical Q&A' started by Octane116, Mar 10, 2004.

  1. Octane116

    Octane116 Rookie

    Nov 3, 2003
    20
    Near Milwaukee, WI.
    Full Name:
    Cliff M.
    I have replaced the exhaust system on my 86TR with a Stainless Borla System and need to know the correct O2 sensor connections. Basically there is one connector with two wires as well as a single wire plug connecto for each sensor.There are two connectors on the right side of the clutch housing that each accept two of the three wires, along with two single connections for the imdividual wires. One connecter is black and one is white. I would presume that the color is done to differentiate left side from the right and should not be mixed up. I need to know, white for right or left? Thanks in advance for the help here!
     
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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,896
    Texas
    Full Name:
    Steve Magnusson
    Cliff -- The good news is that the 2-pin molded connectors are just a +12V line and a ground line to run the internal heaters in the O2 sensors so those can be interchanged with no bad effects. The bad news is that the single spaded (output) wires are bank dependent. Going by the colors will only work out: 1) if they were right in the first place, and 2) if you were sure that you put the O2 sensor that was in the 1/6 position in your old system in the 1/6 position in your new system.
    Do you have a multi-meter? If not, I think there might be a way to sort of wing it (if your TR was running well before the exhaust work), but let me know (I want to minimize my homework!)

    (Can you explain why when disconnecting this rat's nest you didn't mark who was hooked to whom? ;))
     
  4. carguy

    carguy F1 Rookie

    Oct 30, 2002
    3,317
    Alabama (was Mich.)
    Full Name:
    Jeff
    I too would be interested to know how to tell which side is which. I've always suspected that mine may be crossed at times due to erratic behavior of the motor. I've also wondered how to tell when an O2 sensor is bad. I don't want to cause anyone to work too hard (hint....) but this would be good to know. If there was a reference source where I could look it up I'd appreciate it. Can O2 sensors be tested off the car on some "static" way?
     
  5. carlrose

    carlrose Formula Junior

    Nov 25, 2003
    300
    Hi Mr. Green,

    Unless O-2 sensors fail completely, they tend to lose "responsiveness" over time. Can they be tested? If you had an oscilloscope to attach (in series) to connector during "closed loop" might be able to determine fluctuations/second. Not sure what would consitute "good" versus "bad". Definitely "bad" if return a static voltage (while plugged in; this is normal when running "open loop") I have a thread on FT under "328 exhaust popping" showing pictures of propane torch and voltmeter readings of sensor (bench testing). New Bosch are about $130 with wiring, to splice in runs about $20 less from Importec.com.

    HTH,
    :) Carl
     
  6. Octane116

    Octane116 Rookie

    Nov 3, 2003
    20
    Near Milwaukee, WI.
    Full Name:
    Cliff M.
    Steve, I do have a multimeter, and the car was running fine before removal of the system. The exception is that the idle seemed to surge up and down when cold starting the car some times. Although by what I have read and heard with TR's this is not unusual. As far as why I did not mark the wires. No good answer, other than everything else I have taken apart on this car, has always been pretty self explanatory to put back togther. So I thought this would be likewise. By the way, both of the single wires coming from the wire loom are green in color.
     
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  8. henryk

    henryk Formula Junior

    Dec 9, 2003
    479
    Door County, WI
    My 88 TR wiring manual shows the O2 sensor signal going to pin #7, in the large connector, going to the FI ECU. Take the connector off and use an ohm meter between pin #7 and the O2 sensor lead. Try this with both sensors..........the one with continuity, is the proper one. The ECU facing the front of the car, controls the left side of the engine.

    My 86/87 TR wiring manual also has the front FI ECU serving the left side of the engine..........also pin #7.
     
  9. henryk

    henryk Formula Junior

    Dec 9, 2003
    479
    Door County, WI
    BTW: When you look at the large (25-pin) connector, you will notice two rows of contacts........one row has 12 connectors, while the other has 13.

    The #7 pin is the 7th connector, counted from either side, of the 13 pin row.
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,896
    Texas
    Full Name:
    Steve Magnusson
    Cliff -- Just wanted to confirm what Henry posted:

    1) the forward-most injection ECU controls the 7/12 side, and

    2) pin #7 at each injection ECU should be connected to the single output wire from that bank's O2 sensor.

    (See the schematic on pg 74 of your TR OMs for how to figure out who pin 7 is on the injection ECU connectors -- if it's not labeled/molded directly on the connector body itself.)

    I hadn't noticed before, but on the '88 US TR wiring diagram they only give a size ("1"), and no color, for those single (shielded) wires from the loom that go to the O2 sensors -- so can't confirm/deny your "verde" observation.

    (Please ignore this if you're already BTDT, but)
    If you've not unplugged a TR injection ECU before, the connector sort of "hinges" out in a horizontal plane about a hook on the forward end of the connector (after holding "open" the metal clip at the rearward end of course). I've always had to unplug things in order C13, C12, 1/6 inj. ecu, 7/12 inj.ecu -- i.e., I don't think you can just unplug one of the inj. ECU by itself easily.

    Good luck with wrapping up the project...
     
  11. henryk

    henryk Formula Junior

    Dec 9, 2003
    479
    Door County, WI
    My wiring diagram also gives the O2 wire a #1..........but it adds the following: "Schermo" to it. The S is bold, referring to the color pink? The 86/87 wiring manual only gives the #1. The "Schermo" is stated for BOTH O2 sensors, so it would seem that both are the same color...........right and left bank.
     
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  13. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,896
    Texas
    Full Name:
    Steve Magnusson
    "Schermo" I believe translates as "shield" or "shielded" in this case (as in the wire hooked to pin #7 is part of a coax arrangement shielded by an outer braided conductor hooked to pin #8)
     
  14. henryk

    henryk Formula Junior

    Dec 9, 2003
    479
    Door County, WI
    So neither wire is coded for color. I will just have to take a look at mine...........tomorrow.
     
  15. carguy

    carguy F1 Rookie

    Oct 30, 2002
    3,317
    Alabama (was Mich.)
    Full Name:
    Jeff
    Thank You Very Much Steve and Henry. This is great information! I will verify my O2 sensors this weekend. Hopefully they will match up with my labels, since I've unhooked them for the engine-out work.

    Has anyone had experience with a running TR where the sensors where hooked up opposite? If so...what did it do? How did it run? I can see this easily happening since there is no clear indentification between the left and right sides. Could any damage result from them being swapped? If not, just for giggles, I may just switch connections for a few minutes to see what happens...just for my own reference and curiosity.

    I'm now thinking I may want to replace my O2s with new ones just to eliminate that variable.
     
  16. Octane116

    Octane116 Rookie

    Nov 3, 2003
    20
    Near Milwaukee, WI.
    Full Name:
    Cliff M.
    Thanks for all the information fellas. I will run it down this weekend too. Unfortunately I have to get more put back together on the car before I hear the new Borla system. But I am getting anxious! Steve gets an added thanks because he helped me before with a dash removal question. He is an asset to this site!
     

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