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  1. #1

    Default 86 MAF Conversion and O2's / Harness

    So i will try to spell this out in as much detail as I can. First off the car runs and drives, only went on a short trip..and o2's are completely unplugged at the moment until I figure this all out. I have been over as many wiring diagrams as possible and read hundreds of threads.

    My question is simple. On an 86 MAF swap, using all 86 wiring harness's including the 02 wiring, do any changes need to be made to the O2 harness?

    I read all this mess about the jumper loop wire, 6 pin 02 sensors vs our 3 pins, adding a "loop" wire in the 02 harness. Grounding pin 30 to not get a "code 67" and checking pin 47 for voltage at starting / cranking as to not "fry" the ECU's trace wire on pin 46. It just seems NOBODY mentions 86 specifics when talking about MAF conversion and our O2 harness seems to be lacking wires and the NSS is a bit differnt on our cars. Like I mentioned though, it starts, idles and runs okay (needs a tune). I just want to know if I can plug in the O2's and if the ECU will see the signals correctly from them.

    Here in detail is what I have currently done.

    Car is an 86 GT 5 Speed manual, v8 5.0
    Engine is from an 89 Auto, but only used the Engine, A9P ECU and MAF. I DID NOT CHANGE the harness on my car, I left it all 86. Left the 5 speed. tried to steal the new O2 sensors off of the 89 but realized the had a different plug, and I chunked my orig 86 O2 sensors. So in all purposes, this would be a normal 86 MAF conversion using an A9P ecu.

    Added 4 wires for MAF to the ECU (pin 9, 40, 50 and 57)
    Added 2 VSS wires (my car has cruise) to pin 3 and 6
    Added Fuel Pump Relay monitor Wire to pin 19
    Swapped pin 11 to 32 and 51 to 38

    Hopinf someone on here might have knowledge / insight to this subject specific to an 86 GT.

    Thanks all.

  2. #2
    FEP Power Member Ourobos's Avatar
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    In short, no. The O2 differences and loop back you mentioned are only dependent on if you swapped a different tranmission vs. what the body / o2 harness is, i.e. you put a AOD in a T5 car, the o2 harness either sends signal return via the clutch safety switch or the neutral safety switch, and the harness must match that.

    I have done several of these, just did my 86 SSP a few months back. I pinned in the MAF plug, moved the thermactor pins, and wired over to the FP relay as described in the stangnet document. My car did not have cruise, but I elected to wire in a VSS plug as well. Mine runs like a top and gets 20mpg..

    What seems to be holding you up, just scared to plug in the O2? If so and your wiring is all factory, do it to it.
    1986 CHP SSP Coupe

  3. #3

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    Awesome. Im waiting on new o2s. I pulled them off if the 89 and learned the plug was different. Just wanted to make sure when i got it tuned the ecu was getting all the signals from the O2. Good to hear! Thank you. I guess i just did a littke too much reading and second guessed myself

  4. #4
    FEP Power Member Ourobos's Avatar
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    Nah, I've seen folks fry multiple ECUs by hooking them up to the wrong body harnesses. You should be good though.
    1986 CHP SSP Coupe

  5. #5

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    Quote Originally Posted by Ourobos View Post
    Nah, I've seen folks fry multiple ECUs by hooking them up to the wrong body harnesses. You should be good though.
    Cool car BTW. Love these 4-eyed

  6. #6

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    Save your money.

    Unplug the harness off that gt you got in the driveway and switch it out with the one on the 86.

    The 86 o2 sensors don't have the same plug because they aren't heated o2's. However, where the haness plugs into the fuel injection harness, it is the same.

    Now you can just use the 89 plugs on the 86 harness.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  7. #7
    FEP Power Member Ourobos's Avatar
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    ^ Just make sure both cars were equipped with the same type of transmission, as the pin outs you were worried about can destroy the signal return circuit on the ECU if not.. Or you can repin the GT's O2 harness if necessary.. IF you go this route
    1986 CHP SSP Coupe

  8. #8

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    Quote Originally Posted by Ourobos View Post
    ^ Just make sure both cars were equipped with the same type of transmission, as the pin outs you were worried about can destroy the signal return circuit on the ECU if not.. Or you can repin the GT's O2 harness if necessary.. IF you go this route
    Exactly. This is why I didnt do that...AND I sold off the 89 harness to make the money back so its not an option anyway. I didnt want to run into the trouble of accidentally frying pin 46 lead because the 89 was an auto. I ALSO gave my 86 O2s away lol. The 89 had brand new O2's. I didnt know the plug was different. But, Ill just need to pick up some new 86 o2's.

    Thanks all. Helps knowing others have done this and it looks like I got everything right.

  9. #9
    FEP Senior Member Lubner's Avatar
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    Mike ,
    Just stick with the 86 harness in your car. I am running the same set up as you A9P with a SCT chip with no problems making good horsepower.

    Hey man really enjoy your videos too.

    Joe
    1979 Ghia Coupe
    5.0/C4
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    1981 Cobra
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    Bright Bittersweet
    2022 Mustang GT
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  10. #10

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    Quote Originally Posted by Lubner View Post
    Mike ,
    Just stick with the 86 harness in your car. I am running the same set up as you A9P with a SCT chip with no problems making good horsepower.

    Hey man really enjoy your videos too.

    Joe
    Appreciate it man! Good to know your running this combo. I'll stick with it...just need to find 02's

    appreciate all the help guys

  11. #11
    FEP Power Member Ourobos's Avatar
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    Here are the two I put on my 86, like mentioned gets 20mpg and runs like a top :

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    1986 CHP SSP Coupe

  12. #12

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    Mike,

    Just plug in your O2's. You will be fine as you are not swapping transmissions and you repinned your EEC harness.
    Can't wait to see the car running after you have it tuned.
    Did you find a local tuner yet?

    FYI... here are some pics of my 86 T Top..
    68k milles
    bone stock except for a cat back K&N, 3G.

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    1986 GT T Top- stock except for magnaflow cat back
    1990 LX vert- 500hp V3 and all that stuff
    2013 GT- usual bolt ons

  13. #13
    FEP Senior Member OX1's Avatar
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    Quote Originally Posted by mdula View Post
    It just seems NOBODY mentions 86 specifics when talking about MAF conversion and our O2 harness seems to be lacking wires and the NSS is a bit differnt on our cars.
    Read this one yet?

    http://vb.foureyedpride.com/showthre...sion-questions
    86 Capri, 5.0, 5Spd, A9L QH/BE, 47 lb Inj PMAS 3" MAF, Single T44 Turbo, Front Mount IC, TW170,
    Stock Cam, Explr Intake/TB, 1.7 Rockers, CF dual friction clutch, 3" DP, 2.5" full Exh, 3.27, 11.932 @ 115.78
    84 LTD, 331-10:1, TW170/Exprl Intake, 47 lbs inj/80 mm LMAF, Full Duals, Quarterhorse, Vortech 7PSI, Lentech AOD, 5 lug Mk VII brakes/rear, Eibach Sway bars, Cobra HB (dads ride, but I fix it )

  14. #14
    FEP Senior Member OX1's Avatar
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    Quote Originally Posted by Haystack View Post
    Save your money.

    Unplug the harness off that gt you got in the driveway and switch it out with the one on the 86.

    The 86 o2 sensors don't have the same plug because they aren't heated o2's. However, where the haness plugs into the fuel injection harness, it is the same.

    Now you can just use the 89 plugs on the 86 harness.
    They are heated, just the heater ground is through the exh (that is why they
    are 3-wire), see here.

    86 Capri, 5.0, 5Spd, A9L QH/BE, 47 lb Inj PMAS 3" MAF, Single T44 Turbo, Front Mount IC, TW170,
    Stock Cam, Explr Intake/TB, 1.7 Rockers, CF dual friction clutch, 3" DP, 2.5" full Exh, 3.27, 11.932 @ 115.78
    84 LTD, 331-10:1, TW170/Exprl Intake, 47 lbs inj/80 mm LMAF, Full Duals, Quarterhorse, Vortech 7PSI, Lentech AOD, 5 lug Mk VII brakes/rear, Eibach Sway bars, Cobra HB (dads ride, but I fix it )

  15. #15

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    Heated o2's were a mid year change from what I've been told. Mid 86 they were supposedly all heated. I had one car where you could feel when it finally got up to temp and changed fuel strategies. It wouldn't do it at idle.

    Ive had I think 5 86's and ive kept the o2's and harness from a few of them. I have four different connectors between them. I know one of them, I ended up having to order then for a 84 or 85 cfi car to get the right plug. Then there is a square 4 pin connector and a round 4 pin connector. All my 87 up cars were the same.

    Now this is on cougar bird s.o. 302's, but the wiring and connectors are almost identical to a stang of the same year.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  16. #16
    FEP Senior Member OX1's Avatar
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    Quote Originally Posted by Haystack View Post
    Heated o2's were a mid year change from what I've been told. Mid 86 they were supposedly all heated. I had one car where you could feel when it finally got up to temp and changed fuel strategies. It wouldn't do it at idle.

    Ive had I think 5 86's and ive kept the o2's and harness from a few of them. I have four different connectors between them. I know one of them, I ended up having to order then for a 84 or 85 cfi car to get the right plug. Then there is a square 4 pin connector and a round 4 pin connector. All my 87 up cars were the same.

    Now this is on cougar bird s.o. 302's, but the wiring and connectors are almost identical to a stang of the same year.
    Could be, I bought my Capri as a leftover when Aero's first came out.
    So that one would qualify as later than mid-year.

    Could have sworn the original CFI 3.8 harness in my dads 84 LTD had 3 wires though.
    Maybe not, been along time.

    Anyway, I ran for years without that 30 pin connected up, didn't idle for crap cold,
    I always thought it was due to the turbo plumbing and no tune (back them, just
    Cartech FMU and stock inj)............
    86 Capri, 5.0, 5Spd, A9L QH/BE, 47 lb Inj PMAS 3" MAF, Single T44 Turbo, Front Mount IC, TW170,
    Stock Cam, Explr Intake/TB, 1.7 Rockers, CF dual friction clutch, 3" DP, 2.5" full Exh, 3.27, 11.932 @ 115.78
    84 LTD, 331-10:1, TW170/Exprl Intake, 47 lbs inj/80 mm LMAF, Full Duals, Quarterhorse, Vortech 7PSI, Lentech AOD, 5 lug Mk VII brakes/rear, Eibach Sway bars, Cobra HB (dads ride, but I fix it )

  17. #17
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by Ourobos View Post
    Nah, I've seen folks fry multiple ECUs by hooking them up to the wrong body harnesses. You should be good though.

    JACook noted that the late CFi 5.0's had moved to an internal EECIV ECU controlled heated O2 sensor, so you can certainly fry something if the computer and O2 sensor aren;t the same, its not just A9L's and Port EFi computers and O2 sensors.

    Quote Originally Posted by JACook View Post
    The difference between a 3-pin O2 sensor and a 4-pin O2 sensor is ground isolation. Both are heated sensors,
    but the 4-pin type provides a ground wire for the heater circuit, and another isolated ground wire for the sensor
    signal. The 3-wire sensor ground is for the heater only, with the sensor return ground path coming through the
    exhaust system and engine, same as you would have with a 1-wire. As you might imagine, the 4-wire sensor
    can provide a cleaner signal.

    BTW, my late-85 CFI HO vert uses the 4-wire sensor, with the heater circuit controlled by the ECU. So Ford had
    several ways they implemented these things...

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