Fox Body Mustang Mass Air Conversion Installation Instructions (86-88)

Posted 12/8/2016 by Dustin Leathers

Rid your Mustang of that speed density air intake setup with our mass air conversion wiring harness to allow the use of a mass air meter!

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How To Install Fox Body Mustang Mass Air Conversion

Parts & Tools Required

  • Conversion harness
  • Cold air intake
  • Mass air assembly
  • Mass air compatible PCM (Manual transmission cars use a A9L or A3M processor) (Automatic transmission cars use A9P or C3W processor)

Installation Instructions

  1. Remove your negative battery cable


  2. Fox Body Mustang Mass Air Conversion Install

  3. Remove your existing air inlet system, and install a mass air tight induction


  4. Fox Body Mustang Mass Air Conversion Install

  5. Take your mass air meter, and slide it into the coupler, making sure the meter electronics are parallel to the ground


  6. Fox Body Mustang Mass Air Conversion Install

  7. Finish installing your inlet system, and tighten all clamps


  8. Locate the rubber firewall grommet for the PCM harness


  9. Fox Body Mustang Mass Air Conversion Install

  10. Using a long screwdriver, carefully puncture the boot, and remove the screwdriver


  11. Fox Body Mustang Mass Air Conversion Install

  12. From inside the car, find the puncture hole you created in the grommet, and feed the screwdriver through it


  13. Fox Body Mustang Mass Air Conversion Install

  14. Using quality electrical tape, attach the mass air conversion harness to the tip of the screwdriver, making the tape wrap as smooth as possible


  15. Fox Body Mustang Mass Air Conversion Install

  16. From inside the car, carefully pull the screwdriver back through the grommet pulling the wires through


  17. Fox Body Mustang Mass Air Conversion Install

  18. Remove the tape from the harness


  19. Fox Body Mustang Mass Air Conversion Install

  20. Remove your kick panel along with the PCM, and remove the electrical connector from it


  21. Fox Body Mustang Mass Air Conversion Install

  22. Release the 4 retaining tabs, and remove the black plastic harness guard


  23. Fox Body Mustang Mass Air Conversion Install

  24. Using a small pick, or similar tool remove the red plastic pin retainer from the PCM harness plug


  25. Fox Body Mustang Mass Air Conversion Install

  26. Locate the wire running to either pin #37, or #57 of the PCM connector, we used #57

  27. Fox Body Mustang Mass Air Conversion Install

  28. Cut the PCM harness wire and splice in the red wire from the mass air conversion harness into the PCM harness, using a butt connector, or by soldering


  29. Fox Body Mustang Mass Air Conversion Install

  30. Locate the black wire running to either pin #40, or #60 of the PCM connector. We used pin #40


  31. Fox Body Mustang Mass Air Conversion Install

  32. Cut the PCM harness wire, and splice in the black wire from the mass air conversion harness into the PCM harness using a butt connector, or by soldering


  33. Fox Body Mustang Mass Air Conversion Install

  34. Click the pre-terminated tan wire from the mass air conversion harness into the empty terminal location #9


  35. Fox Body Mustang Mass Air Conversion Install

  36. Click the pre-terminated blue wire from the mass air conversion harness into the empty terminal location #50


  37. Fox Body Mustang Mass Air Conversion Install

  38. Locate the white wire, with the red tracer located in the #51 position, and use a tiny pick to release the terminal lock, and remove the wire from the connector


  39. Fox Body Mustang Mass Air Conversion Install

  40. This wire will be snapped into place at empty terminal location #38


  41. Fox Body Mustang Mass Air Conversion Install

  42. Locate the green wire with the black tracer located in the #11 position. Using a tiny pick release the terminal lock, and remove the wire from the connector


  43. Fox Body Mustang Mass Air Conversion Install

  44. This wire will be snapped into place at terminal location #32


  45. Fox Body Mustang Mass Air Conversion Install

  46. Re-install the red pin retainer by simply pushing it back into place


  47. Fox Body Mustang Mass Air Conversion Install

  48. Group the harness together, and re-install the black plastic PCM harness guard


  49. Fox Body Mustang Mass Air Conversion Install

  50. Back under the hood, make a few tape wraps around the mass air conversion harness, to keep the wires together


  51. Fox Body Mustang Mass Air Conversion Install

  52. Route your harness where you'd like it. Pull any slack you need from inside the car


  53. Install the supplied split loom tubing onto the harness


  54. Fox Body Mustang Mass Air Conversion Install

  55. Cut it to length and retain the end with electrical tape


  56. Make a wrap around the harness, route the tape through the split in the loom, and then tape the loom


  57. Fox Body Mustang Mass Air Conversion Install

  58. Plug in the conversion harness to the mass air


  59. Fox Body Mustang Mass Air Conversion Install

  60. Pull any extra harness slack back into the car


  61. To keep everything nice and neat, use a few zip ties to keep everything together


  62. Fox Body Mustang Mass Air Conversion Install

  63. Reconnect the PCM to the harness, and slide your PCM back into place, and re-install the kick panel


  64. Fox Body Mustang Mass Air Conversion Install

  65. Remove the vacuum hose running from the intake manifold to the MAP sensor


  66. Fox Body Mustang Mass Air Conversion Install
    NOTE:
    This will now function as a barometric air sensor

  67. Plug or cap off the open vacuum hose or port


  68. Fox Body Mustang Mass Air Conversion Install

  69. Reconnect the negative battery cable, and double check your work, and you're all done


Fox Body Mustang Mass Air Conversion Install

About the Video

Mustang GT/LX Mass Air Conversion Review & Install (86-88 5.0L)

Check out our YouTube channel for even more tech tips, installation videos, how-tos, and more. The best place to go for anything Mustang related!

Published on 2015-03-10
In this video, JMAC breaks down Pro-M's Mass Air Conversion Harness for your 86-88 5.0L Fox Body!

If you've been around the Fox Mustang community, you have likely heard of a mass air conversion. The necessity of this swap comes in when you decide to change camshafts, increase displacement, changing injector size, or otherwise modify the car in a way the manifold vacuum will be altered.

This mass air meter conversion wiring harness was developed to allow the use of a mass air meter on cars that were originally equipped with a speed density air intake setup. It comes complete with wiring, looming and easy to follow installation instructions.

- Requires use of a mass air PCM
- Some wire splicing is required

Manual Transmission PCMs
- A9L
- A3M

Automatic Transmission PCMs
- A9P
- C3W

Mustang Fitment: 1986 (86), 1987 (87), 1988 (88) - 5.0L GT/LX
Transcript
[MUSIC PLAYING] If you've been around the Fox Mustang community, you've likely heard of a mass air conversion. A mass air conversion pertains to '86 to '88 Mustangs that were originally equipped with a speed density system. The necessity of the swap comes in when you decide to change camshafts, increased displacement, or otherwise modify the car in a way the manifold vacuum will be altered or injector size will be changed.

To perform this swap, you'll need a conversion harness, cold air kit, and a mass air sensor assembly, all available on our website. You'll also need a mass air compatible PCM. For manual transmission cars, use an A9L or A3M processor. And for automatic cars, use A9P or C3W processors.

The difference in PCM versus transmission comes from differences in the O2 sensor harness that can cause PCM failure if the two are intermixed.

The conversion harness we offer comes with printed instructions, so what follows are video highlights of each step in the process.

Before you begin installation, disconnect the negative battery cable. Remove your existing air inlet system and install a mass air-tightened induction, like the cold air kit that we have here.

Take your mass air meter and slide it into the coupler, making sure the meter electronics are parallel to the ground. Finish installing you inlet system and tighten all the clamps.

Locate the rubber firewall grommet for the PCM harness. Using a long screwdriver, carefully puncture the boot and remove the screwdriver. From inside the car, find the puncture hole you created in the grommet and feed the screwdriver through it.

Using quality electrical tape, attach the mass air conversion harness to the tip of the screwdriver, making the tape wrap as smooth as possible. From inside the car, carefully pull the screwdriver back through the grommet, pulling the wires through. Remove the tape from the harness.

Remove your kick panel along with the PCM and remove the electrical connector from it. Release the four retaining tabs and remove the black, plastic harness guard. Using a small pick or similar tool, remove the red, plastic pin retainer from the PCM harness plug.

Locate the red wire running to either pin 37 or 57 of the PCM connector. We use pin 57. Cut the PCM harness wire and slice in the red wire from the mass air conversion harness into the PCM harness using a butt connector or by soldering.

Locate the black wire running to either pin 40 or 60 of the PCM connector. We used pin 40. Cut the PCM harness wire and splice in the black wire, from the mass air conversion harness into the PCM harness, using a butt connector or by soldering.

Click the pre-terminated tan wire from the mass air conversion harness into the empty terminal location number nine. Click the pre-terminated blue wire from the mass air conversion harness into the empty terminal location number 50.

Locate the white wire with the red tracer located in the number 51 position. Using a tiny pick, release the terminal lock and remove the wire from the connector. This bar will be snapped into place at empty terminal location number 38.

Locate the green wire, with black tracer, located in the number 11 position. Using a tiny pick, release the terminal lock and remove the wire from the connector. This wire will be snapped into place to terminal location number 32.

Reinstall the red pin retainer by simply pushing it back into place. Group the harness together and reinstall the black plastic PCM harness guard. Back under the hood, make a few tape wraps around the mass air conversion harness to keep the wires together.

Route your harness where you'd like it. Pull any slack you need from inside the car. Install the supplied split-loom tubing onto the harness. Cut it to length and retain the end with electrical tape. Make a wrap around the harness, route the tape through the split in the loom, and the tape the loom.

Plug in the conversion harness to the mass air. Pull any extra harness slack back into the car. To keep things nice and neat, use a few zip ties to keep everything together. Reconnect the PCM to the harness and slide your PCM back into place and reinstall the kick panel.

Remove the vacuum hose running from the intake manifold to the map sensor. This will now function as a barometric air pressure sensor. Plug or cap off the open vacuum hose or port. Reconnect the negative battery cable, double check your work, and you're all done.

Latemodelrestoration.com is your source for all things related to Fox Mustangs. Be sure to subscribe to our YouTube channel, follow us on social media, like Facebook, and, of course, check out our website for all sorts of awesome Mustang products and content.

[MUSIC PLAYING]