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Thread: A9p, a9l, a9m?

  1. #1
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    Default A9p, a9l, a9m?

    Went the junkyard today and found an '89 Mustang that still had the computer in it -- turns out they had just put the car in the lot yesterday. I have an AOD and this was a manual Mustang. The ECU was an A9M. Scanning the Mustang forums I found one article that says that an A9M was for manual convertibles while the A9L is for notch and hatch. Not sure why convertibles would need to be any different. Apparently there is very little difference between the two. So my question is, can I use this A9M for my bird with an AOD? On the Mustang forums, it says that the mustang O2 harnesses are different (manual vs AOD) and you'll fry your O2 signal rtn if you do that. Is that also a problem on our cars?
    '88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers, welded sub-frame, unlocked digital speedo.

  2. #2
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    I am under nearly 90% confrimed impression that the whole 02 sensor debate is isolated to the wiring of the mustang only.

    Turbocoupe50 is running an a9l on his white bird for years now ,, its an a9l on his aod.

    i plugged up an a9l to my sons 88 bird which is an aod when we converted him to mass air,,, turned out the refurbished eec i got from vinnie tbird played nicer than the a9L,, i think the vinninie one was equal to an a9p.


    i believe this is decently correct for eec options (the a9t was on cop cars only,,, but its nothing special),, the 93 cobra eec isnt all that special either (begines with "X"), from what i have read and been told,, its fairly bottle necked in the programming,, due to the communist state of Ca. ~ cafe)
    auto A9P cw3 8Lf A9T
    manu a9L A9M a9s 8Ld(Ca.)

    then there is some more stuff about this in my diy link below


    good luck,, watching this post

  3. #3
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    Interesting. I'm troubleshooting another problem right now that seems to point to my TFI or dizzy. Once I figure that out, I'll swap out my A9P for the A9M and see if I can notice any difference. Good to know that some folks are using an A9L with an AOD without issues.
    '88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers, welded sub-frame, unlocked digital speedo.

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    A9P has better timing tables.
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

  5. #5
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    I can tell you right now that the EEC doesn't give a flying fart whether the car has a roof or not...

    The O2 sensor wiring is another thing, but as stated, doesn't really apply to a (stock equipped) 5.0 Tbird.

    (because they only ever came with an AOD).

    On MY Sport, once I did the HO and T5 swap, I used an SD1 EEC, thing ran like a taliban with a squad of SEALS shootin at his ass. Or, in other words, as hard as it could.

    On my current car (stang, in signature below) I've changed some things around with an eye to a procharger install later this year. Probably going to use current engine, but I'm prepping a block for a complete and blower friendly build. Lowered compression, etc. It's also got more displacement than a 5.0..
    '84 Mustang, work in (sloooooooow) progress...
    '87 Stang notch
    1994 Ford F150 Flareside
    1997 Explorer V8 conversion (in progress)
    1998 Explorer 5.0
    and a couple of tractors. Ford, of course.
    FORD power, for life!

  6. #6
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    Quote Originally Posted by ThunderbirdSport302 View Post
    I can tell you right now that the EEC doesn't give a flying fart whether the car has a roof or not...

    The O2 sensor wiring is another thing, but as stated, doesn't really apply to a (stock equipped) 5.0 Tbird.

    (because they only ever came with an AOD).

    On MY Sport, once I did the HO and T5 swap, I used an SD1 EEC, thing ran like a taliban with a squad of SEALS shootin at his ass. Or, in other words, as hard as it could.

    On my current car (stang, in signature below) I've changed some things around with an eye to a procharger install later this year. Probably going to use current engine, but I'm prepping a block for a complete and blower friendly build. Lowered compression, etc. It's also got more displacement than a 5.0..
    My understanding from reading the Mustang forums is that the convertibles were lighter so the A9M has just slightly different tables than the A9L -- probably nothing you could detect. You're project sounds like a lot of work but very cool. I'm probably going to buy a crate engine when my finally gives up (might be sooner than later).
    '88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers, welded sub-frame, unlocked digital speedo.

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    Quick update on this thread. I had been chasing down hesitation under load and a backfiring issue when my A9P went out. After changing out the caps, it still wouldn't function properly at key on/engine off i.e. no fuel shutoff signal. I also was getting no spark but that turned out to be my TFI that died after three months. I sent the A9P out to a repair shop on ebay where they won't charge you if it can't be repaired. In the meantime I bought a refurbished dizzy and new TFI. I also bought another A9P off CL to have as a backup in case mine couldn't be repaired. The shop sent mine back and said it was fixed. I put the new TFI, dizzy and computer in and it started up but it still had hesitation/back firing issues. So I tried the A9M from the junkyard -- lo and behold, started up and no hesitation or back firing. I had been working on this problem for six months trying different sensors etc... until my TFI died. Just for grins, I took the A9M out and put in the other A9P I bought from CL. It's never run better. It might be my imagination but the A9P performed better than the A9M -- at least for my car. No hesitation, no back firing just strong, smooth acceleration.

    Learnings:
    My 'repaired' A9P must still have a problem -- the same problem it had before the TFI died and it went into LOS. The A9M works, but not as well as a working A9P. There probably was nothing wrong with my old dizzy (I was thinking it was the Hall effect sensor) so I'll keep the old one as a spare.

    Hopefully all these gyrations will help others on the forum. It's been a frustrating journey. My thanks to all who chimed in.
    '88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers, welded sub-frame, unlocked digital speedo.

  8. #8
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    you said something................

    "ie- no fuel shut off signal"


    are you saying as you typed "the fuel pump remains running while KOEO?
    -if yes...........

    someone by accident or by trial and error was either ...
    A- injecting 12vdc on the tan light green wire at the
    ...1- Self test diagnostic connector
    ...2- Fuel pump relay in the trunk passenger side near the hinge

    which means pin 22 on the eec,, that circuit on the board is fubar. (see my diy link and look into the EVTM,, like 87evtm around page 54 or 55.


    it is very easy to inject 12v on the tan light green wire if while pulling codes the instructions on how to do so were not clear to the person doing the test....
    or...
    while in the trunk trying to force the fuel pump to run by jumpering around the fuel pump relay.

    you can yourself open the eec and trace the run on pin 22 as far as you can till you might find a blown run perhaps?

    if the ebay repair guys are not actually testing for this possibility then they may not find the issue.
    they may have a few levels of diag tests and did a quick test on your eec.

    in theory this is not a problem the general public should ever have so its not really a common fault. its people like us here who generally have this problem because we are technically confident but prone to making simple mistakes with broader odd ball outcomes generating problems rarely seen.


    THe eec uses the tan light such that the eec supplies the "ground signal" reference for fuel pump relay coil.

    i have never studied if adding a diode to the tan light green at the eec would help prevent the problems associated with back feeding 12v battery or not.

  9. #9
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    Quote Originally Posted by jcassity View Post
    you said something................

    "ie- no fuel shut off signal"


    are you saying as you typed "the fuel pump remains running while KOEO?
    -if yes...........

    someone by accident or by trial and error was either ...
    A- injecting 12vdc on the tan light green wire at the
    ...1- Self test diagnostic connector
    ...2- Fuel pump relay in the trunk passenger side near the hinge

    which means pin 22 on the eec,, that circuit on the board is fubar. (see my diy link and look into the EVTM,, like 87evtm around page 54 or 55.


    it is very easy to inject 12v on the tan light green wire if while pulling codes the instructions on how to do so were not clear to the person doing the test....
    or...
    while in the trunk trying to force the fuel pump to run by jumpering around the fuel pump relay.

    you can yourself open the eec and trace the run on pin 22 as far as you can till you might find a blown run perhaps?

    if the ebay repair guys are not actually testing for this possibility then they may not find the issue.
    they may have a few levels of diag tests and did a quick test on your eec.

    in theory this is not a problem the general public should ever have so its not really a common fault. its people like us here who generally have this problem because we are technically confident but prone to making simple mistakes with broader odd ball outcomes generating problems rarely seen.


    THe eec uses the tan light such that the eec supplies the "ground signal" reference for fuel pump relay coil.

    i have never studied if adding a diode to the tan light green at the eec would help prevent the problems associated with back feeding 12v battery or not.

    Could be a blown run. I didn't see anything on the top side of the board but maybe some issue on the bottom. Who knows what they test for.
    '88 Bird 5.0, TW 170s, HO cam, Scorpion rockers, Explorer intake 70mm TB/EGR, MAF conversion, 24# injectors, 8.8 3.73 disc rear end swap, console swap, leather seats, 11" front discs, 15-1 rack, TC springs all around, x-pipe, BBK headers, welded sub-frame, unlocked digital speedo.

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