carlos2405

good morning, I having an issue keeping my motor starting. I found some issues with the fuel pump not working and now I discover some other ones as far as computer changes that the previous owner did. car did not turn on when I bought it. vehicle wants to start then just dies. if I use starter fluid will start but dies fast.
I found some vacuum hoses and other stuff disconnected tape up. also I have another 89 motor and from my 86 that I have issues I notice that the injector harness are not the same a little difference. I being going trough google looking for information and no success as far as what computer and harness this vehicle should have. I have computer and all harness at the moment from my 89 that's under construction.
my wife told me to just pull the motor from this 86 and put my 89 on it but I think this issue could possibly be resolved with out all that higher effort.
I understand that allot of things could be the issue. at this point I will like to know more in depth as far as the harness to injectors and the computer that should be on my car.
NOTE: I seems to me that some how owner had some rodent problem because I found a harness in the trunk completely destroy and some crazy modification or electrical tape on what was installed. that's why I decide to install the one from my 89.
I also use the computer from the 89.
this is the first pic when I got this car 2 months ago

GT Nate

Might look into a Haynes manual for it. Plus there's a big aftermarket for those Fox body cars, perhaps a vendor might have some info.

Looks like a fun project car!

wbrockstar

*** NOTE ***
If youve already installed the 89 harness & 89 EEC into your 86 model,did you also install a maf sensor and maf harness + remove the vacuum hose from the map sensor (behind the upper intake) and plug the hose then leave the vacuum port on the map sensor open to atmosphere?? Your car came with SD (speed density= no maf sensor) from the factory, unless a previous owner or you done a maf conversion on it previously, so if you add a 89-93 maf EEC and maf harness to it,you also have to add a maf sensor/harness + do the things mentioned above related to the map sensor,otherwise the engine wont start.


The main EEC/engine wiring harness + injector harness diagrams,for the 86 & 89 models, are shown below.The injector harness is the same between 86-93 models except for the addition of a diode that was placed on the iac harness wires on all 86-88 models.** The injector harness starts at the black/white 10 pin (aka: salt & pepper) connectors behind the upper intake **
If you swap the 86 injector harness for a 89 harness and youre still using the 86 oem iac valve (which didn't have a diode built into the valve itself) you will have to splice that harness diode into the 89 iac harness wires, unless you swap to a oem 89-93 or remanufactured iac valve (which has a diode built in to the valve) If youre already using a oem 89-93 or remanufactured iac,
the valve can be used with the 89 harness without adding a diode to the 89 harness. Diagrams posted below shows how to identify a iac valve w/ a diode,so just make sure if your iac harness has a diode,dont use a iac valve with a built in diode and vica versa.
So to recap:
86-88 injector harness w/ inline iac harness diode must be used with a oem 86-88 iac (w/out a diode built into the valve) or you can remove the diode from the harness and install a oem 89-93 or remanufactured iac valve (w/ a diode built into the valve)

89-93 injector harness w/out inline iac harness diode must be used with a oem
89-93 or remanufactured iac valve (w/ a diode built into the valve)

If you use a harness that has a diode in it & a iac valve that also has a diode built into it,
it'll cause stalling because of a compatibility issue with the two diodes fighting each other.So check your injector harness and iac valve to see which ones youve got & make sure youve got only 1 diode present,either on the iac wiring harness or on the iac valve itself,but not on both.
*** NOTE ***
All remanufactured iac valves come with a diode built in to them.Using these valves with a harness that has a diode built into it,can/will cause stalling due to the diodes
fighting each other.




88-91 EEC harness pinout




86 EEC harness pinout

89-93 Injector harness



IAC harness diode 86-88 injector harness

wbrockstar

If the engine and everything induction related are the original oem 86 parts,there are a few differences between a 86 & 89 model.The best thing about the 89 engine is valve reliefs on the pistons and better flowing cylinder heads.
1986=
Pistons w/out valve reliefs-less ptv clearance
E6​​​ heads-crappy
58mm throttle body
SD engine management system-cam swaps cannot be done without idle/driveability issues.
1989=
Pistons w/ valve reliefs-more ptv clearance
E7 heads-good
60mm throttle body
MAF engine management system- cam swaps can be done

carlos2405

thanks guys I will work on this info and I will let you know.

carlos2405

wbrockstar

Did you verify whether your iac wiring or iac valve has a diode ?? The diode must be present, either on your iac wiring or in the iac valve itself, but not on both.If the diode is not present on either part or its present on both parts, it will cause stalling.
The following combinations can be used together:
1) 86-88 injector harness + 86-88 oem iac valve
2) 89-93 injector harness + 89-93 oem iac
valve
3) 89-93 injector harness + remanufactured iac valve

* THE COMBO BELOW CAN ONLY BE USED IF YOU CUT THE DIODE OUT OF THE HARNESS THEN SPLICE THE WIRES BACK TOGETHER *
4) 86-88 injector harness + 89-93 oem iac valve or remanufactured iac valve


The 1988 vacuum diagram is shown below.Its the same vacuum route as the 86 model.If the diagram isnt clear,copy/paste the following link into your browser and it'll open the diagram from the site its posted on.
http://www.veryuseful.com/mustang/tech/engine/images/88Stang5.0Vacuum.gif


Identical To 1986 Vacuum Routing

carlos2405

got it I will inspect that I know the harness on the injectors don't have one because I inspect that one, that being said:
I am using my EEC which should be the original.+ EEC harness to all other connections and I know its the original because the harness have all those different color FUSE LINKS and I did not change that only thing I change was the injector harness.
I notice my injector harness from my 89 should come with the diode on the valve notethis car its under construction never had issues with that motor since 2000). so I think the issue its almost done and just follow me:

this is what I figure from the info above u provide me and its really clear on your statement I just try to make sense to my self (thanks)
1986 EEC+1986 EEC harness(color fuse links)+1989 injector harness(no diode because 1989 and over was built on IAC valve) +1986 IAC valve(no diode)....... let me know if this is correct
and thanks for the vacuum diagram its the best I have got. I will save it on my files really appreciated
swapping my IAC valve from my 89 to my 86 should solve this issue as far as harness comparability and function? correct? (hoping no more issues)
thanks again WBROCKSTAR.

wbrockstar

The answer is yes to every question you asked.However, if there are other suspect components on the engine that can cause stalling,the installation of the 86 iac valve might not rid the problem,but if its the only fault on the engine,the original iac valve should solve the stalling.

carlos2405