Mustang Mass Air Conversion

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In this document, I will outline the steps to convert a speed density mustang to the MAF system. I am generating this because I felt the documentation I had to work with could be improved. This is based on my own personal experience converting my 88LX convertible to MAF and the instructions that came with the kit I bought. The color codes of the wiring are what I saw in my car and may not be the same but probably are. This document is for reference only and I accept no responsibility for what you do to your car.

REQUIRED COMPONENTS: You will need to obtain a Mass Air meter, a MAF computer and the electrical harness for the MAF meter. The meter harness can be purchased from several manufacturers for about 50-60 dollars but you can make your own if you wish. There are a few EEC’s that can be used depending on the car. I’ve heard it doesn’t matter manual vs. auto tranny but I don’t know for sure so this is just some additional info for you.

For older MAF computers, the numbers are:
Manual transmission hard top:E9ZF 12A650 AA
Manual transmission convertible:E9ZF 12A650 BA
Automatic transimission:E9ZF 12A650 CA

For later (early 90′s I think) MAF computers, the numbers are:
Automatic transimission:F3ZF 12A650 BA
Manual transmission:F3ZF 12A650 AA
Universal EEC:F3ZF 12A650 DA

You can also use the 93 cobra computer:F3ZF 12A650 CA but it requires MAF calibrated for 24# injectors.

The MAF mounting bracket and associated plumbing between the throttle body and the air filter box will have to be acquired from a junk yard or you can rig up your own setup. If you intend the to do the “optional” signals mentioned later, you’ll also need to obtain 3 EEC connector pins and some wire.

NOTES: Average mechanical skills are about all that is needed. The only special skill I suggest you have to do this conversion is soldering. Crimp connections are unreliable and could lead to future troubleshooting headaches which you should avoid.

Before you begin, disconnect the battery. Remove the passenger side kick panel. There is 1 screw and a push-in fastener that secure it. Remove the screw in the white plastic retainer that holds the EEC in place. There was a ground wire and a relay, each one screw that I had to move out of the way so I could get the old EEC out. You should now be able to pull the EEC down and out. Once the EEC is out, remove the EEC harness connector using a 10mm socket to loosen the bolt in the center of the connector.

You’ll need to run the 4 wire MAF meter harness through the fire wall on the passenger side. I suggest you poke another hole in the large oval grommet the existing EEC harness goes through located in the upper corner on the passenger side of the firewall. I popped the grommet out of the firewall with a screwdriver and used an exacto to poke a hole in the thin section. You don’t just want to blindly jam something through there because you may cut the insulation on some of the wires and cause future shorts. I then used a wire coat hanger as a snake, poking it through the grommet and coming out by the EEC inside the car. I taped the MAF meter harness to the snake (protecting the EEC pins) and pulled it through from inside the car. Pop the grommet back into the firewall after the harness has been pulled through. I then used some silicone to seal the area where the new harness goes through the grommet so I didn’t get any water leaks. Remove the red “H” shaped plastic pin lock in the EEC connector. Gently pry around the plastic pin lock with a pointed awl or small scewdriver working it up and out of the connector. You can’t add or remove EEC pins to the connector without removing this lock. Depending on the MAF meter you have, it may have a 4 or 5 pin connector. Refer below for pin locations.

PIN 5-Pin connector (E4FB 14489 BA) 4-Pin connector (F078 14489 BA,E9DA 14489 BA)
A Power (+) Power (+)
B No connection Ground (-)
C Ground (-) Signal (-)
D Signal (-) Signal (+)
E Signal (+)

a. The Power (+) wire from the MAF meter harness needs to be spliced into the existing red wire in position #37 of the EEC connector.
b. The Ground (-) wire from the MAF meter harness needs to be spliced into the existing black/green wire in position #40 or #60 of the EEC connector.
c. The Signal (-) wire from the MAF meter harness needs an EEC pin which then gets inserted into position #9 of the EEC connector.
d. The Signal (+) wire from the MAF meter harness needs an EEC pin which then gets inserted into position #50 of the EEC connector.

The locations for pin #9 and #50 should be empty. The pin numbers are embossed into the plastic connector on the back of it where the pins insert. It’s a little hard to see but they are there if you look closely.

Please note that the notches shown in the diagram are not the ones seen in the picture. The ones in the diagram are actually keys that only permit the connector to be installed into the EEC one way. Pins 20,40, and 60 are closest to you in the picture. It should be obvious because the pin locations for the additional signals must be empty.

Remove the existing air filter box cover and tube leading to the throttle body. Install the MAF to the passenger side strut tower which should already have the holes for the bracket. Connect the duct work, tighten the clamps and connect the meter to the MAF meter harness.

You will need to move the 2 signals for the thermactor pump to different locations in the EEC connector. The EEC pins are held in place by a hook shaped retainer that snaps into a groove in the EEC pin. To remove you must pry the hook back from the EEC side of the connector and either push on the pin or pull on the wire from the back. I used a paper clip and flattened one end but a small jewelers screwdriver would work also. The wire currently in position 51 tan/red needs to be moved to position 38. The wire currently in position 11 green/black must be moved to position 32. If there is not enough slack for this to reach the new location, you’ll have to splice in some extra wire. Mine reached without doing this.

The next 2 steps some consider optional but will generate error codes in the EEC. Others have reported stalling problems without the VSS signals. In my opinion it’s worth doing if only for piece of mind and no bogus error codes. In preparation for these signals, remove the driver’s seat and the driver’s side kick panel. There are 3 wires that will need to be added for these signals with EEC pins on one end. I suggest you tie them all together and route them as one cable over to the EEC on the passenger side. I took this opportunity to change the carpet at the same time so I had most of the interior out which made this fairly simple.

This signal called FPM2 is used to monitor the voltage going to the fuel pump. It will generate an error code in the EEC if it’s not connected but “shouldn’t” cause a problem. Splice into one of the 2 pink/black wires going to the relay located under the driver’s seat and insert the other end into position 19 of the EEC connector. Refer to figure 1.

Figure 1 (Relay under driver's seat)

These signals are required for cruise control and as stated earlier, some have reported stalling problems on cars not equipped with cruise so avoid the head-ache and just do it. These will also generate an error code in the EEC if not installed. These signals come from a sensor that plugs into the transmission. The easiest place to tap into them is behind the driver’s side kick panel. There is an 8 pin connector cable which runs back to the driver’s seat, across the floor under the seat then back towards the front of the car and then goes through the transmission hump to the sensor. You will need to splice into the orange/yellow wire. The other end of this signal needs an EEC pin attached and this gets inserted into the EEC connector into position 6. You need to splice into the dark green/white wire for the other connection. The other end of this signal needs an EEC pin attached and this gets inserted into the EEC connector into position 3. Refer to figure 2.

Figure 2 (VSS signals behind driver's kick panel)

Put the red H shaped pin lock back into the EEC connector. Bolt the connector to the new MAF EEC and slide the EEC back up in place. Install the bolt for the EEC retaining bracket and any other relays/grounds you may have removed to get the old EEC out.

The manifold absolute pressure (MAP) sensor is located on the firewall next to the vacuum tree. Disconnect the vacuum line from the sensor going to the intake and plug the line going to the intake so you don’t have a vacuum leak. Leave the port on the sensor open and DO NOT disconnect the electrical connection to the sensor.

MAP Sensor on firewall

Congratulations! You should now be done with your MAF conversion. I suggest you re-check all your wiring changes at this point before you re-connect the battery to avoid a smoke show of a different sort. Once you are happy that everything is correct, re-connect the battery and start the car. The car may idle a bit rough for a while until it relearns, but severe idle or drivability problems may indicate a real problem.

Author: Mike Stowe

Categories: Aftermarket, Mustang Tech

36 Responses to Mustang Mass Air Conversion

  1. Kyle 08/26/2009 at 1:30 pm #

    Hey Mike, thank you very much for all this. It was a breeze! I’ve been working on mine for weeks. Got a new wiring harness out of a newer fox and some one told me it was just plug and go. They were wrong! All kinds of shit. I had mechanics, and a ford dealer working on trying to find were all these wires went. Thank you very, very much. I was starting to give up. I do have the cobra eec though. Hooked a buddies gt eec up in mine and it works a lot better. So what exactly do I need to do to get mine to work. Right now I have the stock 19# injectors but I do have I 70mm throttle body and different intake. A msd ignition. Didn’t know if any of this would make a difference? I runs as is now but seams to be running rich at idle. Thanks again! Kyle

  2. tom 08/27/2009 at 12:37 pm #

    thank you for the instructions. my son and i converted my 88lx last sunday. it worked like a charm. i used used parts. all that i had to buy new was the pins to go into the eec connector and some tubing. thanks again.

  3. Mike Knittel 09/20/2009 at 9:02 pm #

    Good article…just one small detail:

    “You can also use the 93 cobra computer:F3ZF 12A650 CA but it requires MAF calibrated for 24# injectors.”

    This is not exactly the case. The Cobra ECM is setup to use 24# injectors, true. However the MAF is not specially calibrated for the injectors. The Cobra MAF, while larger in diameter gives the same signal comparing the same flow as the standard HO MAF. In fact the Cobra MAF can be plugged directly into a standard 89-93 HO setup with no problems. You do however need 24# injectors if you are using the Cobra ECM. The ECM is what is programmed for the injector rate.

    When you see MAF “calibrated” for 24# injectors, what it is doing is skewing the MAF signal to an ECM programmed for 19# injectors but is really connected to 24# injectors. This skewing of the signal fools the ECM into trimming the fuel propoerly in what would otherwise be a mismatch.

  4. chris 09/29/2009 at 2:18 am #

    i have a 88 lx converted to mass air flow, i want my warning lights to work can you help?? i have performer 2 upper and lower intake 24 pound injectors, e 303 cam, cold air, under drive pullys, 70mm, bbk headers, off road h pipe, 373 gears can you help me PLEASE!!!! [email protected]

  5. stangmans 10/12/2009 at 2:25 am #

    just want to know were i can get the EEC pins, im using the plug from my donor car that has already a mass air harness but im just using the plug and the 4 wires for the conversion. THANKS!!

  6. Rob 10/14/2009 at 10:41 am #

    I have an 87 Mustang GT converted to MAF having problems with car running. I have computer for an 89 Mustand Automatic won’t run with that computer. It runs on an automatic computer with NO MAF but it loads up with fuel. Any suggestions on how to get it running. I have a brand new MAF 75mm, motor is a 347 stroker, trick flow heads, trick flow cams, trick flow upper and lower intake. When the car does run but it sounds like it is mis-firing. The firing order is correct… any suggestions?

  7. mraburn 10/14/2009 at 10:44 am #


    To get help I would suggest heading over to our Forums where you can get plenty of tech help.

  8. Andy 10/18/2009 at 3:56 pm #

    Hi. Does anybody know if a 1994 ecu can be used in a MAF conversion? I will be changing my 88 gt to MAF. Thanks

  9. Charlie 10/22/2009 at 2:04 pm #

    Andy, an SN95 (94-95) ecu will NOT work in a fox body mustang, there were too many changes in the smog standards and fuel economy between these two styles of mustangs… is a nice thought, I attempted the same thing, but I had to purchase an ecu from a fox. There are many part numbers that will interchange. And there is ample information available as to which of these part numbers will work in every situation, as always, good luck with your ‘Stang. Light ‘em up.

  10. Brandon 02/03/2010 at 11:40 am #

    Mike, Ive got a 96 3.8 stang and i am trying to convert it to a 95GT ive a 95 wiring harness for the injectors but the MAF connectors are different how could i fix this problem Thanks B

  11. James 02/12/2010 at 5:31 pm #

    I installed a 90 gt (automatic) computer and harness on my 88 automatic, and ever since i thought it would just rev high because i hadn’t plugged the vacuum line from the sensor to the intake, but i did that just now..and after all the months of letting it sit…hoping that would fix it, it didnt. I hear a clicking by the computer panel when i try to turn it over…I see in the above pictures something is spliced in relating to the fuel pump monitoring signal? Could it be that the fuel pump is not giving the engine any gas? Battery is new, fully charged, I have had some problems with I believe the wire coming from the starter, going through some sort of small metal box and then going to the positive side of the battery, but I have replaced that with a similar metal box ( so that it is not directly connected and something “jumps” the gap maybe? , also I have tried just connecting those two wires directly and I still get the same problem…no starting, just the ignigion revving high, and it has been this way since i replaced the wiring harness, and the harness from the 90 was good, it had been in a front end accident before taken out but all wires looked good to me. So again…it wont actually start, it turns over, battery voltage looks good, lights, heat come on…and there is a clicking by the kick panel where the computer is…also the place where the line originally goes from the BMAP to the intake is not “plugged” with a tree-like stint (or is it stent?) of some sort…but by a rubber cap-like-thing, would this make a difference? Please let me know as my little truck is going down the tubes…an 87 mitsubishi…and this is the car i need to be driving now! Thanks for your time- Kevin

  12. donny 05/01/2010 at 4:27 pm #

    i made all the connection as per your direction . now the fuel pump does not come on. any advice would be very welcomed.

  13. Ben 05/09/2010 at 8:14 pm #

    I did these steps and was very happy with the results on my first test drive minus the fact the car wanted to stall but i just assumed that it was relearning. the second drive it seemed severely off like the timing was wrong or it was starving for fuell. still the computer learning or is something else wrong?

  14. cody 06/08/2010 at 12:49 am #

    i bought a c and L 73 mm housing does anyone know where i would get the sensor that goes in the housing from

  15. Timothy Mulvany 10/11/2010 at 8:23 pm #

    This is the best write up I have seen so far. thanks for the detailed information and the pics. Going to make my project that much easier!!!!!!!!!!!

  16. Ray 11/09/2010 at 11:52 am #

    This imformation has help me to know what to buy, to convert my 1989 convertible mustang from density to mass air flow.

  17. Nate 12/03/2010 at 11:18 am #

    I have a 91 Lincoln mark VII auto can you tell me if this MAF conversion will work on it with a EEC out of a 89 GT? thanks

  18. Rob 12/26/2010 at 2:58 am #

    Hi, i have a 88, manual, hatch with 240k on the ODO (rebuilt T5, recent motor rebuild, clutch, 3.73′s w/locker, full exhaust) The motor is stock except for an E303 cam that i did not put in… ive done all sorts of things to get the idle right, but every time it warms up, it hangs around 2k rpm when i try to shift. Will the MAF conversion be a solution or would i be wasting my time/money? I’ve heard a cam without MAF might do that.

    Oh yeah, and after un-taping at least 6 ft of wire total due to short circuits draining batt and fuel pump not working (which is still a mystery, hardwired to inertia switch), found multiple crimp connectors and twist splices (yes, i soldered them) so should i go ahead with the MAF, or continue going through all the wiring for now? Any help is very appreciated, im losing my mind. thanks.

    • Rob 12/26/2010 at 3:00 am #

      PS: It idles fine at a stand-still in neutral..

  19. bill 02/28/2011 at 10:59 pm #

    I just did everything described in the instructions but now is idling very high about 1800rpm???? why any answers would be appreciated. when I push in the clutch it takes a sec for the rpms to fall??? HELP PLEASE!!!

  20. steve 06/03/2011 at 6:18 pm #

    somebody did this car i bought but it has a e9af ecu it runs great when cold but then bad sometimes it runs bad cold .im bout to say forget it n put a carb on it

  21. Blair. 04/23/2012 at 7:56 pm #

    I did the speed density conversion to maf.
    New ford racing 306 with voctech supercharger.
    Pushing 430 fwhp ,370 rwhp with 425 lb,s torque.
    And it was a bloody nightmare…!
    P.S. I’m no electronic wiz.
    Had the harness replaced with maf one .
    Trick flow intake.
    New maf sensor tuned for 42 lb injectors.
    Chip burnt.
    (Note to self should have went carbed as fuel injection mod’s are extremely expensive plus tuning and trouble shooting.)
    Still on the fence about tearing it down and putting a carb on it.
    Car run’s good but it leaves that foggy imagine in the back off your brain (When i have issues down the road be prepared to dumb your wallet)The idea of efi is awesome but carbs are so much easier and don’t need no high dollar speed shop to work on it.
    Just my 5 cents……!

  22. willis fath 10/21/2012 at 8:15 pm #

    actually the best way to convert to mass air is to find a mass air car and use the wiring from it. the best year is probly going to be a late 88 early 89 5.0 mustang.also did you know for the conversion you are talkin about the oxygen sensor wiring harness 89-93 there is a purple wire that loops around back to the plug in and there is one for autos and sticks the wires are looped to diffrent pins on the harness.86-88 non california cars do not have this loop it has something to do with the mass air. if you dont have this loop then you might have drivability problems and they say it could fry the computer.probley would be best to find a 89-93 doaner car that has the correct mass air harnest just make sure the doaner has the same format of transmission auto or t-5.

  23. wayne 06/25/2011 at 4:49 pm #

    would like to change speed dencity to massair i have 1987 thunderbird and is fox body help


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