We're To Get A Rebuilt A9l Computer?

[liljoe07]

What's the voltage at the STI?

 

[Bob91vert]

I'm not sure. I need to find it I guess. Does sti stand for self test input? I did a search and it appears to be a grey connector?

 

[liljoe07]

It's a plug that looks just like the picture I posted. Over by the fire wall and inner fender, on the driver side.

 

[Bob91vert]

2 volts. Thanks for the help by the way.

 

[liljoe07]

Yeah, something is wrong with the computer. The 5v reference voltage is screwed up. You should be seeing 5v on either of the circuits you tested. Is the check engine light real dim looking?

 

[Bob91vert]

yes! And my bud said the same thing. Dim check light, likely computer.

 

[liljoe07]

In this case, he would be correct!

 

[Bob91vert]

Thanks for your help.

 

[jrichker]

The best place to check the 5 volt reference is at the MAP/Baro Sensor. It is on the same wire as the engine mounted sensor like the TPS and EGR.

Look for an orange/wire wire on the MAP/Baro sensor which is mounted on the firewall near the upper intake manifold.

Diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

94-95 Mustang wiring diagrams
Mustang FAQ - Wiring & Engine Info

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/t...ch/engine/images/mustang88VertTopMotorCkt.gif

 

[Bob91vert]

Man you guys really know your stuff. Thanks to all. After the last few days I feel I know this gt pretty good. My last one was a primo 89 gt vert with 62000 original. Never had a hiccup.
This is a triple black 91 vert wit 82000 on it. Way rougher though.
I'll take some pics and post it up now that we have been cleaning, polishing and repairing. It's gonna be our summertime hot rod.
Gonna do 3:73 gears, aluminum heads, new intake, cam, ect. 5 lug 4 wheel disc conversion and some suspension.

 

[Bob91vert]

UPDATE
Got a 87 maf a9l maf computer used for a great price. Plugged it in and vroooom! Thanks to all. Appreciate all the help. Hope I can be as helpful to folks that come looking for answers.

 

[liljoe07]

Sweet!

 

[Grn92LX]

When my a9l died, the fuel pump would not stop priming. Ordered a new (rebuilt) one online for about $100. Quick cheap easy fix.