• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

ECU

  • Thread starter Thread starter D.Piper
  • Start date Start date Jul 21, 2020
Prev
  • 1
  • 2
First Prev 2 of 2

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,827
10,508
203
polk county florida
Jul 22, 2020
#21
  • Jul 22, 2020
  • #21
IMO the easiest way to go is to find a 89 V8 car and swap the wiring, cumputer and cluster to the 87 but since you have some pieces already stuff the 87 wiring in it, get a maf conversion and ride.
Or just run it speed density.
The engine/trans (drive train) is the same from 86 through 93.

What exactly do I need to convert mine to 5.0

Okies folks it's time to make a junk yard shopping list! I have 2.3L 86 mustang LX 2.3 L with an automatic trans (13 screws no OD) I want to make it a 5.0 with Automatic (probably AOD because no computer)(stick is just sucky with me) I know I need a crossmember a K-member, the motor SEFI...
forums.stangnet.com
 
Reactions: D.Piper

Mstng93SSP

You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
2,993
3,500
184
Mililani, Hawaii
Jul 22, 2020
#22
  • Jul 22, 2020
  • #22
I agree. The year of the drivetrain doesn't matter, 87-93 are the same. I also agree you can just run the engine and trans on the speed density setup. Even if there is a mass air meter in the intake tubing it doesn't really matter as it will do nothing with it speed density and it also will not restrict anything. I believe you have to hook up the vacuum line to the MAP sensor on a speed density car. Tha's about it.

Chris
 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Jul 23, 2020
#23
  • Jul 23, 2020
  • #23
T thanks for the help it’s greatly appreciated.
 

Vinnyc1487

Active Member
Jul 14, 2020
106
61
38
Chicago
Jul 25, 2020
#24
  • Jul 25, 2020
  • #24
Why not do what I did with my 87 Gt and get the Holley terminator that’s built for a fox body?? When you find a A9L or a9p ecm and fork over $300 for a 30 year old computer remember the capacitors are only good for 15-20 years and ecm should be rebuilt before placing it in the car. Just a thought to get some newer technology with a much cleaner wire harness for not much more money.
 
Reactions: D.Piper

Vinnyc1487

Active Member
Jul 14, 2020
106
61
38
Chicago
Jul 25, 2020
#25
  • Jul 25, 2020
  • #25
D.Piper said:
So at this point I’ve gotten myself in a situation. I thought I would just need the ECU from an 87 5.0 since my car is an 87 4 cyl but I’m swapping to a 91 GT drivetrain. I bought the car from a guy who has done the entire swap but never finished the wiring. So I ordered a ECU for a 87 5.0 online for 130 dollars but the engine that’s been swapped in already has MAF. So now I’m wondering if I’m out the 130 dollars or if I could switch the MAF to speed density and what would be the easiest way to go.

Are you sure the ecm is for a 5.0??? I have not been able to find a A9L or a9p aftermarket in years they are all discontinued.
Click to expand...
 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Jul 27, 2020
#26
  • Jul 27, 2020
  • #26
Yeah I found it on eBay. It’s not aftermarket it was pulled from an 87 5.0
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,387
2,745
194
Kearney, NE
Jul 28, 2020
#27
  • Jul 28, 2020
  • #27
If in doubt about the capacitors or used computer, the turn around time for ECU Exchange is short, and the service was great. It was also cheaper than a remanufactured one from a chain parts store last time I looked. The pic is a screen shot of them on eBay.

D.Piper said:
Yeah I found it on eBay. It’s not aftermarket it was pulled from an 87 5.0
Click to expand...
 

Attachments

  • 1268EC9A-E0FF-47D2-8E34-991B412DE240.webp
    50.8 KB · Views: 149
Reactions: General karthief and D.Piper

Vinnyc1487

Active Member
Jul 14, 2020
106
61
38
Chicago
Jul 29, 2020
#28
  • Jul 29, 2020
  • #28
7991LXnSHO said:
If in doubt about the capacitors or used computer, the turn around time for ECU Exchange is short, and the service was great. It was also cheaper than a remanufactured one from a chain parts store last time I looked. The pic is a screen shot of them on eBay.
[/Q

The ecu out of an 87 5.0 does you no good that a speed density ecu. You need one out of an 89 or newer hence why you got it so cheap. If it’s not an A9L or A9P you wasted your money
Click to expand...
 
Reactions: D.Piper

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,387
2,745
194
Kearney, NE
Jul 29, 2020
#29
  • Jul 29, 2020
  • #29
I think your message about the 87 computer was for @D.Piper so I hope he sees it.

 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Jul 30, 2020
#30
  • Jul 30, 2020
  • #30
Would it work if I converted to speed density?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,827
10,508
203
polk county florida
Jul 30, 2020
#31
  • Jul 30, 2020
  • #31
87-88 V8 wiring with a speed density computer will work.
See post #21
 

Vinnyc1487

Active Member
Jul 14, 2020
106
61
38
Chicago
Jul 31, 2020
#32
  • Jul 31, 2020
  • #32
D.Piper said:
Would it work if I converted to speed density?
Click to expand...
You can make the v8 part of it work but you will be very limited on your modificAtions in the future. Speed density cars are not friendly on any upgrade that changes engine vacuum especially heads, cam, and intake manifolds there are certainty options for all but they are very limited horsepower gains and really not worth the hassle of changing. The reason I recommend an ecm out of an 89 or newer is so that you can convert your car to mass air and be able to do anything you want to it. Just food for thought my friend
 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Aug 3, 2020
#33
  • Aug 3, 2020
  • #33
Vinnyc1487 said:
You can make the v8 part of it work but you will be very limited on your modificAtions in the future. Speed density cars are not friendly on any upgrade that changes engine vacuum especially heads, cam, and intake manifolds there are certainty options for all but they are very limited horsepower gains and really not worth the hassle of changing. The reason I recommend an ecm out of an 89 or newer is so that you can convert your car to mass air and be able to do anything you want to it. Just food for thought my friend
Click to expand...
Thanks for the advice.
 
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Aug 3, 2020
#34
  • Aug 3, 2020
  • #34
General karthief said:
Using the wiring from the 91?
Click to expand...
What do I do if I use the wiring from a 91?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,827
10,508
203
polk county florida
Aug 3, 2020
#35
  • Aug 3, 2020
  • #35
You have the 87 wiring, 91 had some changes and an air bag.
 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Aug 3, 2020
#36
  • Aug 3, 2020
  • #36
General karthief said:
You have the 87 wiring, 91 had some changes and an air bag.
Click to expand...
The guy said that the wiring in it was from the 91 and there’s a spare harness that he said he thought was from an 87. The problem is, the 91 harness in there is a bit of a mess and a lot of wires ore clipped and it looks really rough. At this point I’m not sure what to do? Should I try and find a new harness? And what year should it be. The ECU in it is a A9l from the 91
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,827
10,508
203
polk county florida
Aug 3, 2020
#37
  • Aug 3, 2020
  • #37
You said you were using the wiring from the 87.
Look, my advice would be to find a 87-88 V8 parts car and get the wiring from it, and the cluster, that way you know what you have, it's hard enough to swap a V8 into a 4 cylinder car without trying to piece together one from unknown, jacked up crap.
If you find a 89 V8 car for parts you get the mass air.
90 up has air bags and several wiring changes between 90-91and 92-93 that can get confusing.
If you can verify that the harness you have is in fact a 87 and in good shape then use it.
 
Reactions: D.Piper
D

D.Piper

Member
Jul 17, 2020
24
3
13
Pleasant Hill, IL
Aug 3, 2020
#38
  • Aug 3, 2020
  • #38
General karthief said:
You said you were using the wiring from the 87.
Look, my advice would be to find a 87-88 V8 parts car and get the wiring from it, and the cluster, that way you know what you have, it's hard enough to swap a V8 into a 4 cylinder car without trying to piece together one from unknown, jacked up crap.
If you find a 89 V8 car for parts you get the mass air.
90 up has air bags and several wiring changes between 90-91and 92-93 that can get confusing.
If you can verify that the harness you have is in fact a 87 and in good shape then use it.
Click to expand...
Okay just one more question, since the wiring changed over the years, would a 89 harness match up to the 91 5.0 or would I have to make some changes? I’d rather run with an 89 because it has MAF and since the engine in it (91 5.0) is MAF I figure that would be the easiest route. My car is an 87 4 cyl swapped to 91 drivetrain.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,827
10,508
203
polk county florida
Aug 4, 2020
#39
  • Aug 4, 2020
  • #39
AGGGGGGGGGGG!!!! ONE MORE QUESTION AND I'LL
just kidding look, stop thinking about the engine being a 91, the engine don't care, if you can find a 89 V8 parts car all the better, if not try to use a 87-88 V8 harness, the 90 through 93 changed wire colors and of course, the air bag, they can be used but extra wires means more work and possibly (at least in my case) more confusion.
Don't make it harder than it has to be.
 
Reactions: D.Piper

Vinnyc1487

Active Member
Jul 14, 2020
106
61
38
Chicago
Aug 4, 2020
#40
  • Aug 4, 2020
  • #40
Just toss in the towel and sell what you have and buy the plug and play Holley terminator kit and save yourself a TON of time and effort plus you’ll never need to worry about wiring or ecm issues in the future. In the long run you’ll be much more satisfied I promise
 
Reactions: D.Piper
Prev
  • 1
  • 2
First Prev 2 of 2
You must log in or register to reply here.

Similar threads

Engine Fuel not pumping
  • Creomod
  • Apr 13, 2026
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
43
Views
695
Fox 5.0 Mustang Tech May 3, 2026
Shakerhood
S
1990 foxbody 5.0 fuel system.
  • staceyj
  • Nov 28, 2025
  • Fox 5.0 Mustang Tech
Replies
8
Views
337
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
F
Electrical Foxbody wiring harness 2.3 to v8 swap
  • Foxbodyjake
  • Mar 23, 2026
  • Fox 5.0 Mustang Tech
  • 2
Replies
24
Views
596
Fox 5.0 Mustang Tech Apr 13, 2026
Foxbodyjake
F
9
Electrical F150 ECU in a Foxbody? Idle surge help
  • 93royalblue
  • Sep 10, 2025
  • Fox 5.0 Mustang Tech
Replies
6
Views
377
Fox 5.0 Mustang Tech Sep 17, 2025
Mustang5L5
Electrical VSS question
  • Mcmahst
  • Nov 22, 2024
  • Fox 5.0 Mustang Tech
Replies
14
Views
435
Fox 5.0 Mustang Tech Nov 24, 2024
Mustang5L5
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?