Converting SD to Mass Air ??

[lx5litre]

I am converting to mass air on my 88 and I purchased a 91 wiring harness. There is a round plug thats beside the main plug in into the computer, I don't know where it plugs into. I am starting to think that it might not be a 91 harness. If anyone can help me out I would appreciate it.
Thanks,

 

[joncash]

Post a couple of pictures if you can. It'll help the people on this board that are familiar with the swap.

 

[Bills89GT]

I just did a v8 swap in my 89 mustang and converted to mass air while i was at it. I used a 91 parts car for the swap and was advised against using that harness because they are not plug and play into any of the pre-1990 mustangs. In 1990 they changed things up with the addition of the air bags. there are many other changes they made through the years but if you find an 89 mass air harness it should be plug and play for you. Another (cheaper) option would be buying the mass air pigtail and installing the terminals to your existing harness. There are many step by step instructions for that swap out there.

Here is a picture of my 91 harness:

 

[lx5litre]

So I guess my next question is, can I still use this harness. I don't have to use the air bag do I?

 

[Bills89GT]

Well I'm not going to tell you it can't be done because it can... but you will have to track down a lot of wires and change the pinouts in some connectors. So it really would not be worth the time and headache. it is not a matter of plug it in and go. it would be much more worth it to spend the time to look for the correct harness or to buy the kit to modify your 88 harness.

 

[lx5litre]

Where do I find this information then??

 

[Bills89GT]

what information are you looking for? to convert the 91 harness or the 88 harness? To get the 91 to work you are going to have to either trace out all the wires and plugs that don't match up or google it and hope you get lucky. Here is a link for step by step install for an 88 harnessMustang Mass Air Conversion | StangNet I was going to try and use my 91 harness too but in the end I didn't feel like hacking it up and wasting a lot of time so i did it the right way and got an 89 harness and plugged it in and it was good. in your case i think the modified 88 harness would be your best and most cost effective solution. If you do get the 91 harness to work please take pictures and post a write up for us so other people can do it too

 

[lx5litre]

Well, the 88 harness is in about 88 pieces Maybe not 88. And try to find an 89 harness isn't the easiest thing. All this crap just for my supercharger.

 

[Bills89GT]

ah well then it should be worth it in the end . this is the guy i bought my 89 harness from: Mustang 89 mass air harness it was a bit pricey but the one he sent me was in great shape.
You could also buy an 88 harness for cheaper and use the harness and the walkthrough i posted to convert it to mass air: Mustang 88 harness