ECM for 92 GT: Is it a A9L? Trouble shooting codes

[skullandbones]

I'm using a donor ECM from a 92 GT. I did not identify the model when I was installing it. This was a GT with the T5 trans. I was thinking the A9L was for an automatic but I've been reading so much about the EMS for fords that I could be confused about that. Any way, the reason I'm checking is I have a surging issue that is happening off and on. So I am trying to trouble shoot it systematically. In one thread they said the A9L was not one of the computers reported to give these kinds of issues (one post).

The vacuum and IAC valve possibilities have been addressed. I just re-installed the upper manifold with new gasket and new gaskets on the throttle body/EGR. I double checked the vacuum lines also (no pin holes or worn ends good tight fit).

Now that I think the mechanical possibilities are taken out, I was wondering if it could be a computer error that would cause the computer to make the engine surge occasionally. I have heard that if you don't hook up the clutch safety switch, and forget to connect the wires together on that circuit, it can cause a error code 67. I haven't checked that out yet but that is my next step: first to see if there is a code 67 and then to check the wiring circuit. It's been so long I have forgotten if I connected those wires together. I used a neutral safety switch on the T5 as my safety instead of the clutch. Normally, I would have addressed the two wires but if I can't remember specifically doing it, I may have left it undone.

If there are no codes on the computer, my next route is to create a continuous power circuit to the PCM across the cutoff switch to maintain the adaptive learning files for computer. I guess it could be that. I have heard various estimates on how long it takes the computer to "relearn" drivability behaviors when the memory is stripped after turning off the battery power to it. I've read thru a bunch of threads on the Mustang forum. The only one with definitive results was the code 67 one.

Thank you,

WEK.

[CraigS]

I am pretty darn sure A9L is a 5 spd ECU. If you are cutting power to the ECU every time you turn the key off, that is absolutely the first thing to fix. There are people who know more details about the
A9L logic than most of us, but I suspect there is no definative answer as to how long it takes to re-learn. I don't think it is a 5-10 minute drive though. Think about it, back in 92 there were probably a few people who knew the answer. And they all worked for Ford. 22 years later, who really knows? The other question is, if there is a code XY, what does that do to how the car runs? Depends on the code for sure, but I wonder if there is a definite answer.

[skullandbones]

The thread I saw with a demonstration of how the code 67 causes surge at idle was done by one of the Mustang gurus. However, he didn't say it was the only code that would cause this problem. So I will have to go there first. If I have multiple codes, it could by cascading effect of the original code. So I will have to start with no codes and try again. Thanks, WEK.

[Jeff Kleiner]

A9L is indeed a stickshift ECU.

Two things:
I recommend that you definitely create a 'keep alive" circuit. What I've done on two cars with battery cutoff switches is simply connect an inline fuse holder across both terminals and plug in a 5 amp self resetting circuit breaker (available at most any parts store):

https://encrypted-tbn0.gstatic.com/shopping?q=tbn:ANd9GcShWzv0RRacrHQryT0iovuUky-3tOZCUbn0iSHFQviM2lfHWA8Xwmt2txd_dBmzq9u4TV4Ew-1D&usqp=CAY

5 amps is more than enough to power up the computer but if something drastic happened to create a big load, such as a failed alternator, it would not reset and you'd still be protected. If you happen to forget to turn the battery switch on and go to start the car you'll hear it buzz then click off---wait a second or two and it resets. I know this because I generally do it about twice a year!

Secondly, if you haven't already done so go through the Ford Racing TPS and idle setup procedure below. I've done this with both EFI cars I've built and in both cases it stabilized the surging idle and low speed bucking.

These steps MUST be performed in sequence!

1. Get engine to operating temperature.
2. Disconnect IAC (Idle Air Control) Solenoid. If engine stalls, turn throttle-stop
screw in one full turn and restart. Repeat as necessary until engine will idle with
IAC unplugged.
3. Set idle using throttle stop. Idle speed will vary depending upon modifications
made to the engine. Set to where you are comfortable with idle speed.
4. Set TPS (Throttle Position Sensor) anywhere from .96 to .98 volts. This is done
by loosening the mounting screws, and lightly rotating TPS. If you cannot obtain
the desired range, you may need to make the mounting holes slightly larger. This
can be done by drilling them.
4a. TPS wire colors to be probed are generally the BLACK and GREEN wire, or the
GRAY/RED and GRAY/WHITE, depending on your vehicle.
5. Stop engine. Disconnect negative terminal battery cable for 15-20 minutes. This will reset the computer to factory defaults. (This is why I recommend setting up a keep alive circuit; without it every time you shut off your battery disconnect switch you're erasing the ECU memory and forcing it to learn again by starting over at square 1 with the default settings)
6. Reconnect IAC Solenoid.
7. Reconnect battery cable to negative terminal.
8. Restart engine.

Good luck,
Jeff

[NICK C]

Jeff, as I look at the pic of the self resetting circuit breaker, is there a female plug that matches it? Or are there different configurations of 5 amp breakers like that. I'm not sure what to ask for at the local Autozone or O'reillys lest they ask me what is it for and what year. I have a Mass Pro fuel injection setup using an A9L and they suggest not to use a battery cut off but I think this will work to keep the memory current. Thanks for the feed back. Nick C.

[DaleG]

Like this, but instead of the fuse, a circuit breaker.
26485

[Jeff Kleiner]

Yep, what Dale said!

Jeff

[NICK C]

Very good. Thanks gents. Nick C

[skullandbones]

That's pretty cool. I thought you would have to fab the circuit for it. Still they will probably ask for what it came on and what year.

I would have to add larger electrical eyelets but other than that it is a simple install.

Thanks for the visual aid.

WEK.

[Jeff Kleiner]

Still they will probably ask for what it came on and what year.



You should be able to find the fuse holder and breaker in the self serve electrical section section of the big box parts stores (Autozone, Pep Boys, etc.). I make it a practice to avoid the counter people in those places whenever possible ;)

Jeff

[skullandbones]

Got it, Jeff! Sometimes I go to that section just to get inspiration, "what could I do with that" sort of thing. But it is beginning to get more populated with stuff you can use such as the contact and wire for a parking/turn signal light. I would have had to replace the whole thing if they had not had a perfect fitting replacement.

Thanks again,

WEK.