91-93 Turbo Swap Wiring Info

Step-by-Step Engine Swap Instructions can be found HERE

91-93 Mustang Turbo Swap Instructions (Updated June 2017)
by Igloo75 & Stinger

If you want a printable checklist while you are doing the swap, left-click or right-click/save-as here (note that printable version may not always be up to date with what is below):
Turbo Swap Instructions

1. Intro

This is specific to the 91-93 LX cars receiving the '87-88 TC computer and VAM harness ONLY. If you insist on running a different ecu (83-86 TC, SVO, Merkur, ect) then you'll have to modify the wiring accordingly. An 87-88 ECU is only $50-75 though and is a much more capable ecu so I suggest you just purchase one of you don't have one. Be sure you also have a big vam (3" in/out) and 35lb fuel injectors (brown tops) to go with it. 

IF YOU DON'T WANT TO DO ANY WIRING CHANGES BUT WANT TO RUN A TURBO ENGINE IN YOUR CAR: Our PiMPx ECU is completely programmable and allows you to run your factory ignition system/wiring with a turbo without doing any of the wiring changes listed on this page. If you want to skip all of these instructions and not have to buy the old 35 year old ECU, air meter, injectors, etc., all of which are limited to around 250hp anyway, while also upgrading to a modern and tunable ECU, you can use our PiMPx ECU and use the DIS (distributor ignition system) components on the turbo engine with the stock DIS harness. Our plug and play ECU's are listed here: Stinger ECU's 

This how-to only requires the use of a small portion of the Turbo Coupe harness (the vam plug and the coil plug). You DO NOT need the entire TC harness as you will be modifying the stock Mustang harness. We sell the VAM pigtail (two versions) here: Pigtails 

These notes are for a 5 speed car only, but should be close if you wanted to do an auto trans conversion. (who would do that)?
I have noticed elsewhere that others have had problems with their airbag systems and the IRCM wiring. With this wiring there is no problems with that.

First off try to use as many pieces as possible from an 87-88 Turbo Coupe, as it will simplify the conversion process. You do not need the whole wiring harness from the t-bird, only a few connectors. you will need the VAM harness connector, the knock sensor connector (I did not use a knock sensor), and you will also need the coil connector.

DO NOT remove the harness from the Mustang.  You ARE NOT using the Turbo Coupe harness in your Mustang.  There are many wires for sensors and modules in the Mustang harness that are not used with the turbo engine, such as the MAF wires and the DIS ignition wiring.

Read this article carefully and you should be set on how to wire the conversion. if you do not understand something feel free to study that area until you do understand. If you do not you could end up messing up something that could be costly to repair.
Also feel free to email me with any questions, or if you find any errors in this article. I will not accept responsibility for anything you might fry in the process of doing this swap. I advise researching all the wiring diagrams and EEC4 info you can get your hands on.

2. Re-pinning the computer

I am not going to explain how to remove and install pins from a connector, if you can't figure it out you might not want to do this swap.  I will give you a hint though, a small screwdriver or small razor knife works well.
SEE CHART BELOW FOR PINOUTS!!!!

3.How to Connect VAM Wiring

To do this part find the MAF connector and cut it off about an inch from the connector (4 wires). Now splice in 3 of the wires from the VAM pigtail to the MAF wires with arrows next to them as follows: (soldering recommended)

Now at the computer move the lt blue/red wire from pin#14 to pin #43
next at the computer move tan/lt blue wire from pin#15 to pin #27
(Both of these steps are mentioned again when doing the rest of the ecu repinning)
note 1: For the 4th VAM wire, you need to run a wire from this to the brown/white wire at the BAP sensor. This is a 5v reference. Don't cut the wire at the BAP, just "T" into it so the final wiring goes to the BAP and VAM. Both the VAM and BAP should have 5v from this wire when wired correctly.

4. Wiring the ignition

The original harness section of the N/A engine is removable from the main portion of the wiring harness. I recommend laying it out on the bench to do this project as this is the worst of the wiring. There may be some questions about this part of the wiring as far as routing of a few of the wires you will need to figure out on your own. I will show you where to connect them.

Once you get the harness section out take all the wire loom and tape off the whole section of harness.

Find the two connectors that originally went to the DIS module (one is black, one is grey)

Now take the TFI ignition module connector from the T-bird wiring and use this as a wiring reference to get the order of the wires correct, as you will be repinning the grey DIS Mustang ignition module connector to match the TFI wiring harness of the turbo motor. This grey connector will plug into the TFI module after the wiring changes.

Wiring from the top of the t-bird connector:
dark blue ---------->(PIP)
yellow/light green--->(SPOUT)
red/light blue------->(crank signal)
red/light green------>(12V ignition)
white/light blue----->(tach, IDM)
black/orange------->(ground)

Now, for reference, the DIS connectors "should" be wired like this in stock form (the colors vary a bit year to year)If the colors don't match, it's ok. The wire LOCATION is what is important, not the colors. If the colors don't match, I'd suggest you write down what your colors are in each position so you can create two wire color columns and number them by position like below:

Grey connector from top:                 Black connector from top:
1-orange/red (foil wrapped)               7-blue/yellow
2-tan/blue                                      8-tan (or pink)
3-tan/green                                    9-blue
4-tan/orange                                  10-grey/orange
5-tan/white                                    11-red/light blue (or blue/tan)
6-tan/yellow                                   12-red/light green

Now you need to remove the pins from both of the DIS connectors above and replace them in different positions into the grey connector as follows. Again, if the colors don't match, it's ok, it's the wire position from the original Grey and Black connectors above that matter:

From top of connector:
10-grey/orange----->(PIP)
8-tan (or pink)------>(SPOUT)
11-red/light blue (or blue/tan)-->(CRANK 12v) this wire needs to be run to the location of the small wire on the top of the starter solenoid, just put a small ring terminal on the end of it and slide it onto the small post on the solenoid. So the final configuration has this wire going from the TFI connector to the small post on the starter solenoid near the coil on the inner fender.
12-red/light green-->(IGNITION 12v) this wire needs to go from TFI connector to the positive side of coil (White)
6-tan/yellow------>(COIL NEGATIVE) this wire needs to go from TFI connector to the negative side of coil (Green)
1-orange/red------>(IGNITION GROUND)

When I did this there is extra wires such as the crank sensor and (leftovers) from the DIS wiring. You can remove the cranks sensor wires and the extra DIS wires. The extra DIS wires could be used for knock sensor wiring if moved to the correct pins at the computer. I opted not to use a knock sensor so I cannot get into details here.  You should be able to eliminate about 6-7 plugs when it's all said and done.  When removing the old coil pack plugs, be sure to connect all of the leftover red/green signal return wires together or you may end up with a no-spark condition and no power to the engine sensors (tps, vaf, bap, etc).

Here is a wiring diagram for the ignition system:

When you are done wiring this little section wrap the harness up with new loom, and tape it up nice.

Note here I used the throttle body from the 91-93 engine to keep from having to change any TPS wires. If you want to use the T-bird throttle body you will have to change the connector.  They are both the same size.  If you choose to use the turbo throttle body (one advantage is it has an adjustable Throttle Position Sensor), here is what I've found as far as wiring goes:

Turbo TPS Plug/Stock 1991 Plug
From Top:
Orange------->Brown/White
Green-------->Grey/White
Red---------->Grey/Red

Be sure to mount the coil behind the battery with the factory mount from the thunderbird.

Be sure to remove the vacuum line from the factory 91-93 Mustang MAP sensor. This makes it a BAP sensor which is what the turbo engine needs to run properly. This sensor is what you ran orange/white VAM wire to at the beginning of this article.

The Mustang oxygen sensor can be used with the TC computer if you swap it into the turbo down elbow where the factory sensor on the turbo engine resides. The turbo ECU is set up for a 3 wire o2 sensor and the Mustang uses a 4 wire unit with integral HEGO ground wire (hence the difference between the 3 wire 87-88 TC o2 sensor and the 4 wire Mustang o2 sensor). The Turbo Coupe has an orange external ground wire that bolts to the turbo. If you want to run the 87-88 TC o2 sensor, one of the alignment tabs will need to be removed to get it to plug in. The 3 wires are in the proper locations, just make sure you follow the instructions for pin 49 in the pinouts listing below to account for the 4th o2 wire.

You will need to use the fuel injector harness from the Mustang so you can plug it into the stock harness.  All the wires are correct.  Make sure you don't use the 91-93 Mustang injectors or fuel rail, they won't work.

Note that you will need to move that ACT Sensor that was located in your airbox to somewhere after the intercooler.  The 87-88 intakes already have them in the back of the lower intake.  You will need to move/lengthen the wires to reach the new location.  I chose to mount mine in the IC tubing right before the throttle body. If you're running a PiMP ECU or other aftermarket ECU, it is best to mount the ACT in a location that's less likely to heat soak when the engine is idling, or has been shut off while hot. This would mean the upper intake is a better location than the factory lower intake location, and in the intercooler tubing after it leaves the intercooler but before it gets near the engine would be ideal. This way the sensor outputs accurate air temp readings under all conditions.

Also note I did not use the coolant temp sensor that is located in the t-bird intake manifold, I kept it in the location it is in originally in the Mustang (in the heater hose). You will need to do this as well to get the fan to function.

If your base turbo engine is a 83-86 model you will need to rig up your own fuel lines from the rail to the steel lines located near the bell housing.  The stock mustang ones will not work.  The 87-88 cars hook right up to the stock lines.  I chose to cut the lines out of the turbo coupe and then cut them to the length needed for the mustang.  I then slid the factory style connectors into the plastic fuel line (may need to smooth out ends of connections with grinder and then lube to get them inserted all the way) and then used two small hose clamps on each one to keep them from leaking.  If was the cheapest/quickest way I could find to fix the problem. Plastic fuel line repair kits are available from most parts stores that allow you to make the lines just like they came from the factory without using hose clamps. This is the best option.

If you want to have a functioning octane switch (a toggle switch that modifies the timing map for premium and regular fuel), you'll need to install a toggle switch and wire it so it grounds pin 24 to put it in premium mode and removes the ground for regular mode.

Here are the pinouts for the computer swap:

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