Mass Air Swap, Quick ?'s

[gadget73]

if you want to, send me your ECM and I'll see if it works in my car. I'm running an A9M as well, so if it works for me, you'll know what the issue is.


When I did the mass air swap in my car, I actually harvested another ECM harness and modified it. My thinking was that if something went badly wrong, I could simply swap the harness back and chug on down the road. I actually kept the SD ECM and a complete wiring harness in my trunk for a couple of months.

[pantera77]

if you want to, send me your ECM and I'll see if it works in my car. I'm running an A9M as well, so if it works for me, you'll know what the issue is.


When I did the mass air swap in my car, I actually harvested another ECM harness and modified it. My thinking was that if something went badly wrong, I could simply swap the harness back and chug on down the road. I actually kept the SD ECM and a complete wiring harness in my trunk for a couple of months.

That's be awesome if you could, I don't have another mass air comp obviously and spending another $100+ just to test it seems a bit silly. I'll play with it a bit more tomorrow, but don't expect anything better.

I figure it's easy enough to swap back to SD for the time being. I can leave the VSS wires I added, so I just need to remove the 2 pins for the MAF (and snip the power and ground for it), and re-switch the 2 for the smog bs. At least all the holes that need to be made in the stupid plastic cover will already be there.

[zoomie]

hey before you go sending this this thing back to the barn or what not, let me run this by doug vanstrom and bob kennedy and see what they think, im sure it probably something silly, also i had a thought are the MAfs you have calibrated forthe injectors that you have? give me a ring tomarrow ill see what i can dig up for ya

[Crownvicman289]

You could just pop the DA1 back in there and leave the MAF and VSS hooked up, right? I've got VSS wired up to my DA1 which I did in anticipation of the MAF swap that I now don't want to do if I don't have to. I also cracked open the case to verify which pins to and do not have stuff going to them. There was a little discrepancy between what was posted online and what I found. One such discrepancy is that pin 34 on my DA1 does run my fuel econometer.

[86VickyLX]

A9M is manual correct? There are wiring differences between the manual and the automatic. Mostly on the start circuit.

[86VickyLX]

As for the current issue...you're not still running a vac hose to the MAP sensor are you? MAP sensor becomes a BAP sensor with MAF swap. I've also heard of O2 harnesses plugged in to the opposite sensors and apparently that causes some serious idle/performance issues as well.

Good luck,
Don

That will not affect how it runs. Because the computer knows that 159hz is way too out of range to be a proper reading and throw on the light. I forgot to disconnect my vacuum line, and that's what my computer did. As for the O2 harnesses, I think that's where they have the start wiring tied in, it's grounded on the manual, power supplied to auto.

If you're swapping auto, to auto computer, the wiring harnesses are the same, electronically...
Auto to Manual, I've seen some issues with cars running like complete shit. And rewiring it, doesn't fix the problem (computer go bye bye).

[pantera77]

A9M is manual correct? There are wiring differences between the manual and the automatic. Mostly on the start circuit.

According to FFI,
A9M 5.0 89-93 Mustang MAF / Auto

Plus gadget is running one so IDK.

[gadget73]

A9M is an auto trans ECM.

You probably could leave the MAF wires in place and just unplug the MAF itself with the SD ECM in there. It might set stupid codes regarding the smog solenoids not being there but nobody really cares about that. Might be worth physically unplugging them anyway if the wires to them are going to the wrong pin on the SD ECM.

a MAF meter is NOT calibrated to anything unless its some nonsense aftermarket part. In stock form, the MAF only produces varying voltage depending on how much air is being sucked through it. the ECM has a table that translates voltage to a specific airflow. This is called the transfer function. The ECM also has a data bit in there somewhere with the size of the injector in it. If you have a programmer, changing to a 24# (or whatever) is as simple as plugging a new value into the injector size data field. If you're running a MAF other than what the ECM expects, that can be fixed by uploading a new transfer function table. The real trick of it is to be able to create the table, and then have a programming tool to feed the data to the computer. The aftermarket "calibrated" meters feed some whacky voltage to the ECM so it thinks its getting less air than it really is, which allows an un-tuned ECM to work with non-stock injectors. Its far from an ideal way to make it work, but it does work.

[Crownvicman289]

The start circuits are very different. On an auto EEC, 12V is split off the starter solenoid and fed into the EEC. I believe there is a diode in the EEC between that pin and pin 46 to prevent this voltage from reaching that ground. When 12V is not applied to the circuit, that pin grounds itself via pin 46. On the manual EEC's, this diode is not present and all it seeks is continuity to ground through the pin that, in the auto, would receive 12V cranking. I did a shitty job explaining it, but manual EEC in an auto car is the only time this could create an issue and often times the EEC is tolerant of it and doesn't die.

[86VickyLX]

Ok. The car runs exactly the same whether or not there's a MAF plugged in? If you can't run a self test, KOEO selftest to be precise, that computer is dead.

[pantera77]

Ok. The car runs exactly the same whether or not there's a MAF plugged in? If you can't run a self test, KOEO selftest to be precise, that computer is dead.

Nope, and I'm not talking running shitty or shittyier. There was absolutely no change between any of the 3 (including one known good 55mm from my BB 92, or having it unplugged. Also, no self test would work, the engine light never came on, and manually putting a light in the Self Test Out resulted in a bulb that was always on. Still, I'm surprised the comp could still somewhat make an effort to run the vehicle.

:cry: Needless to say, this is why I never buy things from eBay. Oh well.


It's back to SD now, and well it's still not running like a champ, it is back to running how it was.

[86VickyLX]

Fail! That sucks mang. If the KOEO (engine not running) test didn't work, then yeah that computer is dead.

[gadget73]

hey if you're coming to Scottfest, bring it with. I'll stick it in my car just for S&G but its probably dead. I wouldn't be opposed to trying my hand at rebuilding one, just in case its something as simple as failed capacitors. If I was starting with an ECM that did not work, its not like I could make it worse.

[86VickyLX]

hey if you're coming to Scottfest, bring it with. I'll stick it in my car just for S&G but its probably dead. I wouldn't be opposed to trying my hand at rebuilding one, just in case its something as simple as failed capacitors. If I was starting with an ECM that did not work, its not like I could make it worse.

I'd be interested in seeing how this turned out.

[pantera77]

Just an update, bought a A9P, and it works perfect. This thing has never ran better. I really can't explain how much better it runs all around. No more pinging issues, idles so much better, no more hesitation on tip in, no more popping through the intake, no more stalling when putting it in gear, everything is so much nicer. It feels so much more powerful too. Can't wait to see what it can do now.