Auto ECU vs Manual ECU

[freshtiva]

I need to put a new engine bay wire harness in my newest car. Its a 93 GL auto with factory A/C. Ive got a wire harness off of a 1991 L manual with dealer add on air. Isnt there a difference in the Auto and manual ECUs ? Will the auto ECU work with the manual harness and if not can I use the manual ECU with the manual wire harness on the Auto car ?

Next questions, would it be worth the trouble ?? Looks like a lot of man hours I dont have. Anyone want a temp job ? All the plug ends are labeled and Ive got several festiva to look at for comparsion.

[skeeters_keeper]

I've got a more or less complete wiring harness for an auto (have an auto ECU too if you need it) that I would like to trade you for the manual harness! I need a manual harness, and have no need for the auto one.

I can send you a pic if you'd like so you can see what all I have. No wires were cut.

[freshtiva]

Could you post a pic of your auto ECU so I can compare it to my manual ECU ? Mainly the plug end and the tag on the ECU.

[skeeters_keeper]

auto left, manual right:

[freshtiva]

Wow, thanks Nate ! So they are different and not interchangable. I wonder what the internal difference is. People do auto to manual swaps seemingly w/o issue.

[FestYboy]

that's because the ecu never sees the trans... so it doesn'tmatter what you have in it

[freshtiva]

True, so why the different ECUs ?

[25Horseplay]

The auto has different timing and fuel curves. Mustang guys used the auto ones for more advance and fuel in the early days before useing computer chips.

[Gomez]

my 90 L+ auto had a B376 and my 93 L 5 speed donor also had the B376

I guess the fact that it doesn't see the tranny tells me that MY power/fuel consumption problems are not ECU related which also goes inline with all the comments here that say it doesnt matter which you use

[jglutz]

The ECU sees the ATX and MTX. One of the ECU inputs is grounded for both.
MTX for Nuetral and Clutch
ATX for Park or Nuetral.
This allow the ECU to adjust the idle mixture/curve.

Looking thru both the factory Service and Electrical Manuals there is no mention of different ECU's. I do not have a copy of the Ford Powertrain Control Module book. to double check.

In the manuals i did look at...1992...the pin outs are all the same for ATX and MTX.
Looking at Skeetr's picts and that the headers are keyed differently...I'm wondering if the are form different years or Carbed and EFI?

[skeeters_keeper]

once again, auto left, manual right.



The insides are different (auto ECU has an additional large IC, and twice as many pins on the IC 601 which I believe is the main control).

Like Brian said, I *think* the only differences between the auto/manual ecu's would be fuel and timing maps, but then why such large internal changes? It would seem like the only real changes needed should be in the maps, not the hardware.

anyone?

[skeeters_keeper]

Joe, you must have posted just before I did.

I can vouch that both of the above were removed from FI festivas, just one was auto and the other was manual. However, one was an 89 and the other was a 91 (89 auto's were FI).

[25Horseplay]

The 89 Auto had its own completely different EFI system. The 89 spark advance was vacuum controled and 90 and newer spark advance was electroncally controlled.

[freshtiva]

The auto has different timing and fuel curves. Mustang guys used the auto ones for more advance and fuel in the early days before useing computer chips.

So would a manual festiva perform better with a auto ECU ? Which I guess would require a auto engine harness too. Does the ECU see the ATX kick down switch ?

[25Horseplay]

The 89 auto one will only work with the 89 auto. I am not sure if the 90 and up are different or not.