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Mustang GT/LX Mass Air Conversion Review & Install (86-88 5.0L)
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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
Automatic Transmission PCMs
Mustang Fitment: 1986 (86), 1987 (87), 1988 (88) - 5.0L GT/LX
[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.
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