Harness Qustion?

[NoStang]

K, my plan is to put the drivetrain from an 88 T-Bird TC into my 81 coupe.

My question is, how much of the 81's original wiring can I keep? If I add just the engine harness and ECU can I get it to work with my ignition and lights and whatnot?

I'm pretty ignorant when it comes to wiring and electrical.

I do have a complete 91 4 banger stang that I could swap the whole chassis harness into my coupe if necessary but I really want to keep the stock dash.

[mfpmax]

The lights and what not are independent of the ECU harness. You tap into two or three wires from the ignition parts to wire into the 88 T/C harness.

A 91 harness is another thing altogther since those too require rewiring to use the 88 ECU...nothing with the dash should be touched if the swap is done properly.

[NoStang]

So which engine harness should I use? The one from the TC or repin the one form the 91 4-banger?

I know that sounds like a stupid question but when people swap the turbo into a regular 4 banger I've read you should keep the harness and just repin it.

[mfpmax]

Someone probably would suggest that the 91 harness would have less "other" crap on it but I honestly have no idea. You have a harness that may be near drop in versus repinning the 91 harness( www.stinger-performance.com has info on that). But I have never seen a 91 harness but do know that both of them have relay boxes...which make things easier. That is of course if you grab those relay modules that go with each harness.

[NoStang]

Well, I still have the TC so I can take what ever I need/may need from it.

Is the relay box located under the hood...don't recall seeing it.

[mfpmax]

Yes, its on the passenger side strut tower I think if I remember correctly.

[NoStang]

K, I finally got the under hood harness out today...what a huge mess of wires!!

So since I won't be needing the ABS/adjustable susp. ect. and I'll be using the stock 81 harness for the lights/horn/wipers ect. can I just remove those parts of the harness?

I didn't see any relay box under the hood.

[TurboBeater]

You can keep the stock dash and interior wiring/external lighting wiring. I combined an '87 t-bird harness with my '83 capri harness. Actually, I did this twice so I could make a nice harness without making the same mistakes I did the first time. There is a TON of wiring in the t-bird that you will not need, unless you want to try to put the abs and ride control on you mustang (and I'm guessing you don't want to do that.

First off, if you don't have a service manual for you mustang or t-bird, you need to get BOTH. Preferably a Chiltons manual and not the Haynes, as the one has more detail and info than the other. Do not start out by just cutting wires unless you know where they go and what they are for. I made this mistake my first time around. As far as wiring for the engine on the 2.3, most of what you need will be coming out of the firewall on the passenger side of the car. If you remove the passenger side kick panel, you will find the engine computer (EEC.) Any wires running into this, you are going to want to keep, with the exception of maybe only a couple wires. All these wires are going to the engine, the relay module (small black box on the passenger side strut tower, near the turbo. There's a bundle of wires running into it,) and the speed sensor under the car on the side of the transmission. Make sure you get all these. You may need to remove the plastic casing on the harness so you can more easily follow the wires from one place to another, but be careful not to fully unravel the harness or you will have a huge mess. Just remove the casing and keep things bundle together using zip ties or a little electrical tape. Besides these wires, most everything else is stuff you don't need. As far as combing the t-bird harness and you old one, you need to connect the t-bird alterneter wires, and the t-bird gauge wires to your old harness. It's maybe only a total of about 4 wires that need to be connected between the two harnesses, give or take a few. It takes a while, but it's doable. Get a cheap multimeter if you don't have one. It will help big-time in tracking down wires and such. You will also need to use a fuel tank and fuel pump from a stang that has fuel injection. Not sure if '81 used a different size tank as the later stangs though. You'll have to search for that on the forums for that. The attached image will be you biggest help. I still use it all the time. I found it on the web, but can't rememeber the site. this link should also help: http://www.rothfam.com/svo/reference/

Be patient with it, because it will be worth it in the end.

[mfpmax]

Speed sensor wires aren't required, but I believe it is needed for certain items. I don't have my VSS connected however. The alternator wires are not required unless you wish to convert over to the newer style alt.

[NoStang]

Thanks Beater, I already have the ECU and harness out of the car. That link should help.

What is the VSS used for, is that what the car uses instead of a speedo cable?

[mfpmax]

Depends on the car. On cars with mechincal speedos its often used with cruise control. On later cars its used for electric speedos. There may be something in the ECUs that use it as well, but I haven't read anything showing such. I know mine isn't hooked up since that is extra wiring I didn't feel like trying to route and wire up.

[TurboBeater]

If it's worth anything, I don't have a VSS either. I cut it out with everything else when I built the car, but I'm wishing I had cruise control considering the 360 mile drive between home and school. It's only a couple wires anyway, and it's easier to retain it rather than put it back. It's up to you though. If I knew then what I know now, I would have kept the ABS, ride control, and everything else. But, that is a ****-load of wiring and stuff. I have a trash bag that weighs about 50 lbs. with wiring in it that I didn't use to make the capri a 2.3T. You won't need the VSS to drive your stock speedo. Your stock speedo uses a cable. My '86 used both, but the VSS was just for the cruise control and emissions stuff. I *think* the VSS might have some control over the charcoal canister purge. Not sure what else.

[Mad Max]

From what I've read the VSS is helps to control the idle. If there's no signal from the VSS the computer assumes the car is stationary and idling. When there is a signal(a given numer of pulses per min. to equal 1mph) the computer will lower the idle to help with decelleration. If computer doesn't know what to do it will hold it's idle position. Its not as important on standard car but on autos it can make them stall just as the car is coming to a stop due to load vs rpm.

[TurboBeater]

Sorry about the crappy diagram I posted. Here is the website with some better sized diagrams: http://www.google.com/imgres?imgurl=http://www.flemworld.com/Slug/Howto/Images/TCWD.jpg&imgrefurl=http://www.flemworld.com/Slug/Howto/8790T.html&h=1556&w=1236&sz=215&tbnid=dxc7oi2QFsgJ::&tbnh=150&tbnw=119&prev=/images%3Fq%3Dturbo%2Bcoupe%2Bwiring%2Bdiagram&hl=en&usg=__SXUlB4OxhnksCr1N-bG6_q8VkLs=&sa=X&oi=image_result&resnum=1&ct=image&cd=1