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  1. #1

    Default Correct ECM for 1986 5.0 EFI mustang GT manual

    Hi guys,
    Does anyone know the correct ECM computer for a 1986 5.0 EFI mustang GT manual transmission car? My car has the VJ1 computer, which with some searching is the 86 auto computer. I found a list of ford computers online, and more than one computer came up for my car. VM1, VP1, VR1, and VH2. Which computer should I get? Which one would have the most performance? What is the difference between these computers? I did not convert the car to MAF, all the wiring is SD.
    Thank you for the help.

  2. #2
    FEP Super Member 86capriASC's Avatar
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    I have one in the spare car. I can dig it out later if you need. What are you looking to find out?
    Mike

    1986 ASCMclaren #108
    stock short block, Victor EFI, 75mm TB, 3.08's, Borla cat-back, slot style MAF conversion, Gt-40p heads, TFS1 cam, 80lb injectors, 69mm turbo, Moates Quaterhorse, E85. 501/584 @ the rear wheels

  3. #3
    FEP Power Member Vinnietbird's Avatar
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    DA1 is the best.
    '88 T-Bird Sport Twisted Wedge heads,3G,,Trick Flow R intake,Scorpion rockers,Ed Curtis cam,BBK headers,Mass Air with 24's,X-Pipe, Flomaster mufflers,75mm t-body,T-5, MGW shifter,Mach 1 chin spoiler,Bullitt gas lid,deep Cobra R wheels,Taurus fan,3.73 gears,140mph speedo,CHE control arms, custom Hood with ''72 Torino scoop, custom trunk lid with integrated spoiler

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    FEP Power Member 4eyegt's Avatar
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    The stock computer in my 86 GT 5 speed is a VM1. I have it laying in the floor since I went with the one from the 88.

    I believe the DA1 is from the 87-88 models. I think I swapped to that and really can't tell any difference.

  5. #5
    FEP Power Member
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    I think I also had a VR1, but it could have been a VM1. Can't remember. Different calibrations annotated different processors.... Most people just use the DA1. Plentifull to come by.

    Jason

  6. #6

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    I think I should refine my question. Which computer is correct for the 1986 GT EFI with T5?
    86capriASC
    I am trying to find out why my idle hangs at 1000 rpm. I was reading that the auto computer and manual computer are different. They both sense when the engine is under load or not by using the neutral gear switch (manual) or neutral drive switch (auto). So the idle is kicked up when the computer thinks the car is in gear/under load. The previous owner made the auto to t-5 swap, left the auto computer and hacked the clutch/tranny/reverse wiring. So I believe the car thinks its in gear when its not resulting in the hanging idle. I tried to verify this circuit in the 1986 EVTM manual, and it let me down. Wiring circuit was not in there, but it mentioned in the 1987+. I have the 86 emission/engine diagnosis manual and its mentioned in there. I got frustrated because the 86 wiring is unique and EVTM sucks. I'm a GM guy, so I'm struggling with my first Ford. Love this mustang cause its different from all the aero mustangs out there! Yes I did see the post on the 86 wiring but it didn't help me. So I bought all the wiring (front headlamp/O2/dash/tranny harness) from a 86 efi gt manual tranny car. Waiting for it to come in the mail so I can swap it in but need the right manual tranny computer.
    Sorry for the long winded reply. I tried to verify the original equipment of the car, but the vehicle certification label is missing (not original doors). I also want to be able to check engine codes, but if this neutral gear switch is not hooked up it will pop a code 67 and not allow further testing.
    Will other things cause an idle problem, yea. Radical cam, but have no idea what is in there now. Vac leak, checked out ok. Salt & Pepper shaker connectors, cleaned them up and tightened them. Idle doesn't surge, just hangs.
    Check engine codes. Can't at the moment, have car ripped apart, but I will.
    Sorry just trying to get my car to function as a Factory 1986 GT 5.0HO w/ T5 would function from Ford.
    Thanks for the help guys.
    Last edited by 454scotty454; 01-04-2010 at 10:14 PM.

  7. #7
    FEP Senior Member ttopmustangs's Avatar
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    my 86 has the DA1

  8. #8

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    My 86 GT with 5 speed has a VM1
    Last edited by toddly; 01-04-2010 at 10:26 PM. Reason: forgot to add 5 speed
    1986 Mustang GT fastback
    1986 Mustang GT convertible
    1980 Mustang Cobra
    1998 Mustang V6 (son's beginner)

  9. #9
    FEP Power Member 4eyegt's Avatar
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    The computer I pulled out of my car (86 GT 5.0 T5) was a VM1. That was the correct computer for my car. The issue you may find is the lack of being able to narrow down to just one specific computer for your specific car. From what I have read so far it seems that even if you limited your search to just the computers for 86 T5 5.0 you would still have 4 or 5 to choose from. Unless one of the Four Eye Masters on here has some info in regards to computers and build dates and plant location and alignment of the moons and well you get the idea. I'm not even sure Ford kept those kind of records back then.

    The VM1 or any of the other 86 5.0 manual transmission computers will work just as good as the next. My car, when stock, had idle surge up to 1100 rpms after any speeds above 55mph. I currently deal with minor idle surge and idle hang but not as bad. I switched to a computer from an 88 5.0 5 speed car and that seemed to help.

    One of the major draw backs to the 86-88 5.0 was the speed density system, referred to as SD from here on out. A vacuum leak will cause idle issues as well. Your issue may not be computer related but in fact could be a vacuum leak or even a cam that is too radical. With SD too radical could be almost every aftermarket cam. Very few cams seem to work with SD.

    Just what I've read on here anyway. Hope that sheds some light on the subject. I'm sure I'll be corrected if I made any mistakes.

  10. #10

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    Thanks guys!
    I just want to restore the car back to factory specs to get a baseline. See how the car acts, then modify. The car was molested before I got it. I was thinking of doing the MAF conversion, but would like to sort out my wiring issues first before any more mods.
    Thanks again guys. I appreciate the help.
    Scott

  11. #11

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    Any cam with more than a 114 degree lobe seperation just do not work with SD. SD sucks unless you are running a stock long block, with maybe some minoring porting to intake etc.
    1986 Ford Mustang LX Notchback
    1980 Ford Mustang Ghia Hatchback
    1998 Honda Shadow 1100 Aero
    2002 Ford F-250 XLT Superduty

  12. #12

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    VP1 here with a T5 trans

    The auto and manual are different. The calibration is different and so is the O2 wiring harnes. If you use auto ECU with a manual o2 harness you will fyr one of the traces in the ECU.
    Last edited by 86GTFox; 01-06-2010 at 03:01 AM.

  13. #13
    gtluke
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    The stock 86 computer is terrible, get one from an 87-88. I noticed a change in performance right away.

  14. #14

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    The spark tables are different in the DA1 form the VP1 and thus the performance gains can be felt. Then again the turbo swril heads on the 86 were junk to begin with.

  15. #15

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    OK here's my .02. The reason there are so many EEC-IV processors for any number of vehicles, is because of the calibration codes. You may be able to find that code on the tag on one of the valve covers. It,s a paper tag. As far as the idle concern, try this, disconnect the IAC valve and see if the engine stalls. My guess is it won't change. If that's the case, go through the procedure for setting the base idle. Actually running an auto processor is benificial in that it has a better timing curve and fuel tables because it came from a car with an auto. Ask me how I know. Good luck, and let us know how things work out.

  16. #16

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    Yes you are correct. The reason for all of the different catch codes (is DA1, VP1) is because of the emissions in different states. Some are updates to others too.

    Not sure about the Auto performing better. I would need to look at the timing tables and fuel tables.

  17. #17

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    I definitely with let you guys know what the problem is. I received most of the correct 86 gt manual car harness in the mail. I read about the O2 wiring frying computers too.
    I should have all the wiring in by this weekend. I am planning on going down to the shop and seeing what I figure out then.
    Will keep you posted.

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