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Discussion Starter #1
I have an 85 Mustang GT with the CFI/AOD in it right now. I am keeping the AOD in it. I have everything I need to convert it to mass air SEFI from a 93 GT 5spd. The computer I have is the A9L. Will it work?? I know the A9P is the best for my application, but I get mixed opinions on the whole A9L or A9P with the AOD. Will the A9L work ok???? Thanks.


Justin
 

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Yes, the A9P has a more agressive timing table over the A9L. And since you are using a non electricial controlled AOD it will make no difference. You will need to rewire the two connectors by the drivers side, that feed the dashboard components. By the the way the colors on the wires do not match.
 

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Discussion Starter #3
What two connectors by the drivers side??
 

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Sorry jsut one, it's an eight pin (brown) connector. I replaced it with two flat four pin connectors from Auto Zone. Also, if I remember I had to rewire the green connector by the PCM. I think it was the O2 sensore power supply (oragne wire.)
 

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I believe that uscggruski is referring to the 8 brown pin connector found near the master cylinder, however, the response seemed quite vague, and I am uncertain how this helped answer your question. While this connector does play into the overall picture of the potential concern for what you are doing, this is not technically the proper location to correct the problem. You just need to make sure that you have the correct O2 sensor harness.

There is a circuit in the previously mentioned brown 8 pin connector that ultimately feeds pin 30 at the computer, which is the Neutral SENSING circuit. An automatic computer (A9P) uses a 12V START signal, while the manual computer (A9L) is tied in with the 5V signal return signal.

Both of these circuits are routed to the computer through the O2 harness. There is a single looped wire (either Purple/Yellow or Blue/Yellow depending on the year of your harness) in this harness that is looped. One side goes directly to the PCM at pin 30, the other side of the loop goes to either the 12V signal or the 5V signal depending on the harness you are using.

The potential problem is as follows. If you are using the A9L (manual) computer with an O2 harness that is intended for the A9P, you will feed 12Volts into the computer at pin 30. Since this particular computer is only intended to receive a 5V circuit, you will damage the computer. It will still run, but you will lose many key features such as the adaptive fuel strategy, and the keep alive memory may no longer function.

The bottom line to your question is that YES you can use the A9L for use with an automatic trans, but just be careful that you have the O2 sensor harness properly configured. THis circuit can be completely removed with no adverse effects on the ability of the computer to function properly, though you will lose the ability to get the trouble codes from the computer while the engine is running. These codes will still be available through the "Key On Engine Off" Continous codes anyway, though.
 

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Discussion Starter #6
Ok, I have the O2 harness for manual trans. I pulled everything out of a 93 GT 5spd. So can I just use that harness? What to do about the Neutral Safety switch since it won't be connected?


Justin
 

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I have compared the A9L tune to the A9P tune.

The difference is that in the low rpm's the A9P has more ignition timing advance (by 10*) than the A9L.
The extra advance was given to the A9P to help the performance of the AOD from a stop.

Using an A9L in an AOD Mustang will sacrifice that 10* of timing at low load / wot.

The timing difference at high load/wot is 1*, which is not significant.

I say find an A9P -
Avoid all the wiring crap
Get the 'best' performance

jason
 
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