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1993 LX 5.0 dies after ignition parts replacement

  • Thread starter Thread starter Warhorse85
  • Start date Start date Aug 16, 2025
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Mindseye007

10 years still blowing strong
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Aug 26, 2025
#81
  • Aug 26, 2025
  • #81
Warhorse85 said:
So I circled the capacitors. The one circled in red has 37k ohms of resistance. The one circled in blue has 622 ohms of resistance. The one circled in yellow has 5.6k ohms of resistance. Now in the close up photo of the backside of the ECM, the object I have circled in red has 3.5k ohms of resistance
Click to expand...
I think you should have the A9P ECU because your car is automatic...might solve your issue.
 
W

Warhorse85

Member
Jun 17, 2023
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Aug 26, 2025
#82
  • Aug 26, 2025
  • #82
Mindseye007 said:
I think you should have the A9P ECU because your car is automatic...might solve your issue.
Click to expand...
So that ECU is actually a reman one. The factory tag was covered up with a solid white sticker to hide it and the was a sticker that was added that had a barcode, part number and said reman on it. I have a feeling that at one point it was for a manual trans car but was reprogrammed or they used the case from one car and the guts from another car. The car has been running fine unit a month and a half ago and I've had the car for 3 years
 
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Warhorse85

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#83
  • Aug 27, 2025
  • #83
Mindseye007 said:
I think you should have the A9P ECU because your car is automatic...might solve your issue.
Click to expand...
So I contacted my local Ford dealer and gave them the VIN and they told me there is no difference between the A9L and A9P because the transmission is controlled by vacuum
 

Mindseye007

10 years still blowing strong
5 Year Member
Oct 21, 2020
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Aug 27, 2025
#84
  • Aug 27, 2025
  • #84
Warhorse85 said:
So I contacted my local Ford dealer and gave them the VIN and they told me there is no difference between the A9L and A9P because the transmission is controlled by vacuum
Click to expand...
The A9P This is a common ECU for 5.0L mass air automatic transmission models.
AOD Transmission: Models with the AOD transmission, such as the automatic 5.0L Foxbody, commonly use an A9P ECU.
 
Last edited: Aug 27, 2025

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
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Aug 27, 2025
#85
  • Aug 27, 2025
  • #85
Mindseye007 said:
Then why do all foxbody automatics come with a A9P ECU?
Click to expand...

I vaguely recall that there were some differences in the strategy between the Auto and the Manual.

Either ECU will run either trans setup — people swap them all the time.
If you run an A9P in a stick car, it’ll work fine, just a touch smoother.
If you run an A9L in an AOD car, it’ll work but shifts can feel harsher because the ECU isn’t pulling timing where the A9P normally would.
 
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Warhorse85

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Aug 27, 2025
#86
  • Aug 27, 2025
  • #86
Noobz347 said:
I vaguely recall that there were some differences in the strategy between the Auto and the Manual.

Either ECU will run either trans setup — people swap them all the time.
If you run an A9P in a stick car, it’ll work fine, just a touch smoother.
If you run an A9L in an AOD car, it’ll work but shifts can feel harsher because the ECU isn’t pulling timing where the A9P normally would.
Click to expand...
The reman A9L is much cheaper than the A9P too
 

AeroCoupe

lube between the nut and the face. I know my lubes
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Aug 27, 2025
#87
  • Aug 27, 2025
  • #87
I know that you have to repin the O2 harness if you put an A9L into an original automatic car. I would inspect the O2 harness and make sure it is correctly pinned for your application.

Post in thread 'Help Reading CEL Light'

Jun 8, 2025
Not having it pinned correctly fries ECUs. You can’t stick a 5-spd ECU into an original AOD car without repinning it first.

Needs to match the below diagram based on year and ECU.



More info here

  • Mustang5L5
 
Reactions: DadLife0724 and Mindseye007

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
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polk county florida
Aug 28, 2025
#88
  • Aug 28, 2025
  • #88
Warhorse85 said:
So I contacted my local Ford dealer and gave them the VIN and they told me there is no difference between the A9L and A9P because the transmission is controlled by vacuum
Click to expand...
Pretty common answer for a tech that has no idea unless a scanner is involved.
 
Reactions: DadLife0724, 5.0specialist, Mindseye007 and 1 other person

Trogdor

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Sep 10, 2025
#89
  • Sep 10, 2025
  • #89
Warhorse85 said:
So I contacted my local Ford dealer and gave them the VIN and they told me there is no difference between the A9L and A9P because the transmission is controlled by vacuum
Click to expand...
I thought the transmission was controlled by a TV cable.
 
R

rwordenjr

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Sep 12, 2025
#90
  • Sep 12, 2025
  • #90
Warhorse85 said:
The reman A9L is much cheaper than the A9P too
Click to expand...
No update?
 
P

Praetorious

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Sep 13, 2025
#91
  • Sep 13, 2025
  • #91
Trogdor said:
I thought the transmission was controlled by a TV cable.
Click to expand...
It is, that guy at the dealership is confused,hes thinking of transmissions before the AOD like a C4 and C6,i quit calling Ford about things with my Mustangs along time ago being that they are 30 plus years old, its like calling Boeing and asking question about the Wright flyer,after reading this whole thread it does sound like the computer has or is going south,i think the poor car had a rough life before its current owner and its starting to show it and act up, mismatched parts and awful things like that.
 
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Warhorse85

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#92
  • Oct 25, 2025
  • #92
Ok everyone, I sent the computer out for a rebuild and they were able to repair it. I sent it to fox mustang restoration and they told the there were many issues with the computer that are now fixed. Just got it back into the car and still cranks but no start. Has fuel but has no spark.
 
R

rwordenjr

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#93
  • Oct 25, 2025
  • #93
Warhorse85 said:
Ok everyone, I sent the computer out for a rebuild and they were able to repair it. I sent it to fox mustang restoration and they told the there were many issues with the computer that are now fixed. Just got it back into the car and still cranks but no start. Has fuel but has no spark.
Click to expand...
Will die on the tfi/pip hill.
 

Mindseye007

10 years still blowing strong
5 Year Member
Oct 21, 2020
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Oct 25, 2025
#94
  • Oct 25, 2025
  • #94
Warhorse85 said:
Ok everyone, I sent the computer out for a rebuild and they were able to repair it. I sent it to fox mustang restoration and they told the there were many issues with the computer that are now fixed. Just got it back into the car and still cranks but no start. Has fuel but has no spark.
Click to expand...
Did you check the tfi? That's what happened to me got the ecu back and my car would still crank and not start. Bought the Motorcraft TFI plugged it in and my car fired right up...ran beautifully.
 
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rwordenjr

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Oct 25, 2025
#95
  • Oct 25, 2025
  • #95
Mindseye007 said:
Did you check the tfi? That's what happened to me got the ecu back and my car would still crank and not start. Bought the Motorcraft tfi, plugged it in and my car fired right up...ran beautifully.
Click to expand...
He did but people don’t seem to get just how bad the reliability is on brand new tfi/ pip parts. I have gotten numerous bunk brand new tfi’s out of the box from multiple manufacturers. By the way, you can actually test your tfi with a multimeter.
 
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Warhorse85

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Jun 17, 2023
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Oct 25, 2025
#96
  • Oct 25, 2025
  • #96
Mindseye007 said:
Did you check the tfi? That's what happened to me got the ecu back and my car would still crank and not start. Bought the Motorcraft TFI plugged it in and my car fired right up...ran beautifully.
Click to expand...
It has a new tfi in it but I was thinking of putting the factory on back in it and see what happens
 

gkomo

now i can hopefully expect to receive the shaft
Aug 2, 2024
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Oct 25, 2025
#97
  • Oct 25, 2025
  • #97
I haven’t swapped my TFI yet but I can attest to them not working out of the box. I bought a Motorcraft one as a backup and a TFI tester. First one couldn’t get the tester light to illuminate, exchanged it for another and it did get the test light to light up. I also tested the second one with a DVM… should have tested the first one but I didn’t know you could do it at the time.
 
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Warhorse85

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Oct 25, 2025
#98
  • Oct 25, 2025
  • #98
gkomo said:
I haven’t swapped my TFI yet but I can attest to them not working out of the box. I bought a Motorcraft one as a backup and a TFI tester. First one couldn’t get the tester light to illuminate, exchanged it for another and it did get the test light to light up. I also tested the second one with a DVM… should have tested the first one but I didn’t know you could do it at the time.
Click to expand...
When I was reconnecting the battery, the wrench slipped and touched both terminals briefly and sparked. Could I have popped an ignition fuse? If so where is that located so I can check it
 
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Warhorse85

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Oct 25, 2025
#99
  • Oct 25, 2025
  • #99
rwordenjr said:
He did but people don’t seem to get just how bad the reliability is on brand new tfi/ pip parts. I have gotten numerous bunk brand new tfi’s out of the box from multiple manufacturers. By the way, you can actually test your tfi with a multimeter.
Click to expand...
Reinstalled the factory TFI module, still no spark. If I unplug the SPOUT connector, I get spark but still won't start
 
R

rwordenjr

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Oct 25, 2025
#100
  • Oct 25, 2025
  • #100
Warhorse85 said:
Reinstalled the factory TFI module, still no spark. If I unplug the SPOUT connector, I get spark but still won't start
Click to expand...
Tfi is not involved if the spout is disconnected
 
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