I found your great write up on ebay guides on the swap, according to that with the 88 s/d eight pin plug on the o2 you can do a straight swap, it is very informative so i figured i would post it for anyone needing a complete explanantion on the swap and o2 issues, ill double check my plug after work but i think i have a 8 and not a 5 pin connector
FOX MUSTANG SPEED DENSITY MASS AIR HARNESS GUIDE
By: neomustangs( 655)
7 out of 7 people found this guide helpful.
Guide viewed: 645 times Tags: Mustang|Fox Body|Mass Air|Speed Density|5.0
BEFORE WE GET STARTED. PLEASE IF THE GUIDE WAS HELPFUL TO YOU AT ALL CLICK THE "YES" BUTTON BELOW AND RATE IT PLEASE. THANK YOU!!
This guide is basically written about fox body mustang harness's. The engine harness in specific. Theres a lot of sellers selling harness's and speculation out there on what harness fits what cars and what years were the right years to use on your 4cyl swap or just to repair the blown or burned up harness in your mustang. This is aimed at 87-93 cars only... 86 and 94-95 are not my foretay so i will not touch that topic at this time. I will gladly add or edit any legitamate information that someone would like to provide me. This review isnt for you to criticize or pick apart. The information i have put on this review is simply for those people that just dont know about these harness's. What one to buy, replace or use in their specific situation. I felt the need to write this review because i see a lot of these people on ebay selling parts and misrepresenting the items they have for sale. Some may do it unintentional, some may be clueless and some just plain dont care. Lets get started....
MASS AIR HARNESS'S ARE NOT CREATED EQUAL. I am not trying to tell any seller reading this how to sell on ebay or suggesting anything of the sort. But when listing your items you should know more about it and label it appropriately versus just misrepresenting a title and selling the wrong harness to the wrong person. Most likely that harness will get returned anyways so why deal with that headache or take that chance? Not all mass air harness's are created equal and you probably already know that. You should pay attention to features on your harness, or tag them what year they came out of and then store them in your bins. Labeling the harness 87-93 in your title is misleading and theres a lot of good buyers out there looking to convert or replace their harness's that may buy your harness and just be frustrated by the outcome of plugging it in and it not working. According to ebay thats your fault for "item not as described" and as of the past year ebay has hammered down on that. No one wants to pay good money for an item, wait to have it shipped only to find out it dont work with their car. Thats SUPER frustrating and as a seller you should avoid that. IMO if your parting the car out you probably already know better... One final note before we get started. IF YOUR DOING A 4CYL SWAP IN A FOX MUSTANG YOU WILL NEED TO REPLACE THE COMPUTER, THE ENGINE HARNESS AND THE FRONT HEADLIGHT HARNESS AS WELL TO PROPERLY DO THE SWAP. ALL V8 FRONT HEADLIGHT HARNESS'S SHOULD WORK JUST FINE 87-93 AS THEIR WAS NO DIFFERENCE BUT YOU SHOULD LOCATE THE PROPER HARNESS FOR WHAT YEAR YOUR CAR IS. IF YOUR 4CYL WAS A 1990, BUY A 1990 HARNESS. IF YOUR 4CYL IS A 1992 BUY A 1992 HARNESS ETC.
87-88. Lets start here. The 87 mustang fox body 5.0 cars were pure speed density cars. This is the second year of the EFI fuel injection system and the complete make over from the 86 style interior and exterior. Some features of the speed density harness is the 2 cannon plugs near brake booster. One should be gray and the other is black. What i mean by "near the brake booster" means where that part of the harness would sit if installed. Also another feature of a pure speed density harness is theres no provision for a mass air meter plug. Basically this would be located near the 02 harness cannon plug as well as the wide open throttle (WOT) AC cutoff relay. So just looking at those 2 things can pretty much tell you what kind of harness this is. Now moving on, in 1988 there threw a monkey wrench in the mix with the engine harness. Now an 88 harness will work just fine in a speed density 87 OR 88 car no problems with the DC or the DA1 speed density computers. However 1988 was the first year for emissions in California so pending on what the production date was for that 88 mustang harness depends on whether the harness got the extra plumbing provisions for the 02 harness. This will also effect rather the harness can be converted to mass air or not too. What am i talking about? 02 Harness plugs. 1987 if you look at the backside of the female 02 harness cannon plug that is found on the ENGINE HARNESS (not the 02 harness itself) you will see 5 wires. The cannon plug im talking about is the actual plug that the 02 harness PLUG INTO aka the female part. Sense 1988 was the FIRST year for the mass air harness for cars sold in CALIFORNIA only, your 1988 car can actually already be equipped with the 8 wire 02 female cannon plug found in all mass air cars but still be speed density. It will work just fine. Whats all this mean? 1987 can NOT be converted to mass air by just running the 4 wires, changing computers and moving the other 2 wires as found in many write ups. Why? Because 1987 didnt have the proper plumbing for the 02 harness signal return that the mass air computer needs. Also the 02 harness didnt have the jumper loop to provision this change found in all mass air cars. Lets put this in a situational basis. You have an 87 and wanted to convert to mass air. Well forget about it. Either buy an 88 speed density harness with the 8 wire 02 plug or buy an 89 mass air engine harness. Because all 89 5.0 cars came equipped mass air. If you wanted to convert your 88 to mass air engine harness you would have to first check to see how many wires are on your female cannon plug on the engine harness. If theres 8 you can proceed as normal. If theres 5 then forget about it. Just get an 89 mass air harness. Sure you could spend the time to plumb the other 3 02 harness wires but its more of a pain than you think. IF YOUR GOING TO CONVERT TO MASS AIR MAKE SURE YOU CHANGE THE 02 HARNESS WITH THE ENGINE HARNESS AS WELL. JUST RUNNING 4 WIRES AND A METER ISNT EVEN THE HALF OF IT. CONFUSED YET? LOL
The 1989 Mass Air Harness. Simply put, in 1989 all 5.0 cars were converted to mass air harness. This was the same exact harness that could be easily used in 1987 and 1988 cars with no issues. This can NOT BE USED in any cars past 1989. Just 87-89 ONLY. Its simple to identify. Of course it had the natural gray and black cannon plugs near the brake booster. It has the oval mass air plug near the WOT AC cut off relay and 02 harness female connector found on the the passenger side inner fender skirt apron. It also has the 8 pin female 02 harness plug and now came with the jumper looped 02 harness for that specific transmission signal return. Whats a signal return? Well its just that, its a jumper loop monitor wire that is solid purple with a yellow stripe on it. If you take your 02 harness apart from the engine harness and peel it back about 2 inches you will see it will "loop" back to the cannon plug and return to the ECU that way. Not having the proper 02 harness for the ECU thats installed and specific transmission in the car can lead to BIG problems with the ECU including frying a trace inside the ECU. It will also be a TUNING NIGHTMARE as most tuners wont even get the 02 harness to communicate with their tuner programs, data log or anything.
The 1990 Mass Air Harness. Well this year started some big changes to the fox mustang. We are lucky to even have 1990-1993 fox mustang as they were almost replaced by the failure of a car the FORD PROBE. So naturally they did some changes to the cars interior. The exterior pretty much was identical but the engine harness were NOT. 1990 engine harness started the provision for the air bags. So they moved some wires in those two cannon plugs near the brake booster. The gray and black plugs that are found in 87-89's that we spoke of previously. So with that being said, this will only work in 1990's mustangs exclusively. It will NOT work in 87-89 or 91-93. What a pain in the arse right? Well at least im taking the time to write this for you, so you can only blame yourself when you buy the wrong harness and see it not work right. It will also plug and play with all 4cyl swap cars that were equipped with 1990 original equipment ie the dash harness ETC.
The 1991 Mass Air Harness. Well guess what folks, they changed the harness AGAIN!!!!!!!!!! Yep, 1991 will ONLY WORK WITH 1991. Whats the biggest feature differences in 1991 compared to the others? Easy. Remember that gray and black 8 pin cannon plugs near the brake booster? Theres only 1 plug there now. And its brown. The black plug moved to the ECU side of the harness, it can be found down near the ECU. Also as the 89 and 90 had in their harness's, of course the 91 had the oval mass air plug on the passenger side fender apron. The big brown cannon plug found near the brake booster was the same in 92 and 93 as well. However how would i tell the difference between 91, 92 and 93 then? Easy again... and i will get to it. Basically if you have a mustang engine harness that has 1 big brown plug near the brake booster and black plug near ECU then its either 91-93. Now to tell the difference between the 91, 92 and 93 go look at the passenger side fender apron part of the harness. In 1991 there will only be the oval mass air plug, the WOT AC shut off relay, the white cannon plug for air bag passenger side and finally the large 8 pin 02 female connector for the 02 harness. Thats all..... if theres an extra relay there... its not a 1991 harness..... moving on..
The 1992-1993 Mass Air Harness. Well finally got to the end of the line. Simply put 1992 and 1993 harness' will work together no problems. None of the previous harness's will work at all. The reason being is because of one major change in the harness and car itself. Basically the 1992 and 1993 harness's are the same as the 1991 harness with one added feature. The passenger side apron of the harness got ANOTHER relay. This is the fuel pump relay. So how do you tell if you have a 92-93 harness? Just look at the passenger side apron and you should have the following: Oval mass air plug, white cannon plug (4 pin) for air bag, Large 8 pin female connector for 02 harness, WOT AC shut off relay, and finally the new provision being the fuel pump relay itself was moved here too... Usually has a "white" cap on the relay. So the plug isnt all black like the AC shut off relay. 91 was the last year they had fuel pump relays under the drivers seat. They were moved to this location in all the engine harness's 92-93.
Guide ID: 10000000175794707Guide created: 06/17/12 (updated 10/12/12)